Network Working Group F. Dawson
Request for Comments: 2445 Lotus
Category: Standards Track D. Stenerson
Microsoft
November 1998
Internet Calendaring and Scheduling Core Object Specification
(iCalendar)
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
Abstract
There is a clear need to provide and deploy interoperable calendaring
and scheduling services for the Internet. Current group scheduling
and Personal Information Management (PIM) products are being extended
for use across the Internet, today, in proprietary ways. This memo
has been defined to provide the definition of a common format for
openly exchanging calendaring and scheduling information across the
Internet.
This memo is formatted as a registration for a MIME media type per
[RFC 2048]. However, the format in this memo is equally applicable
for use outside of a MIME message content type.
The proposed media type value is 'text/calendar'. This string would
label a media type containing calendaring and scheduling information
encoded as text characters formatted in a manner outlined below.
This MIME media type provides a standard content type for capturing
calendar event, to-do and journal entry information. It also can be
used to convey free/busy time information. The content type is
suitable as a MIME message entity that can be transferred over MIME
based email systems, using HTTP or some other Internet transport. In
Dawson & Stenerson Standards Track [Page 1]RFC 2445 iCalendar November 1998
addition, the content type is useful as an object for interactions
between desktop applications using the operating system clipboard,
drag/drop or file systems capabilities.
This memo is based on the earlier work of the vCalendar specification
for the exchange of personal calendaring and scheduling information.
In order to avoid confusion with this referenced work, this memo is
to be known as the iCalendar specification.
This memo defines the format for specifying iCalendar object methods.
An iCalendar object method is a set of usage constraints for the
iCalendar object. For example, these methods might define scheduling
messages that request an event be scheduled, reply to an event
request, send a cancellation notice for an event, modify or replace
the definition of an event, provide a counter proposal for an
original event request, delegate an event request to another
individual, request free or busy time, reply to a free or busy time
request, or provide similar scheduling messages for a to-do or
journal entry calendar component. The iCalendar Transport-indendent
Interoperability Protocol (iTIP) defined in [ITIP] is one such
scheduling protocol.
Table of Contents
1 Introduction.....................................................5
2 Basic Grammar and Conventions....................................6
2.1 Formatting Conventions .......................................7
2.2 Related Memos ................................................8
2.3 International Considerations .................................8
3 Registration Information.........................................8
3.1 Content Type .................................................8
3.2 Parameters ...................................................9
3.3 Content Header Fields .......................................10
3.4 Encoding Considerations .....................................10
3.5 Security Considerations .....................................10
3.6 Interoperability Considerations .............................11
3.7 Applications Which Use This Media Type ......................11
3.8 Additional Information ......................................11
3.9 Magic Numbers ...............................................11
3.10 File Extensions ............................................11
3.11 Contact for Further Information: ...........................12
3.12 Intended Usage .............................................12
3.13 Authors/Change Controllers .................................12
4 iCalendar Object Specification..................................13
4.1 Content Lines ...............................................13
4.1.1 List and Field Separators ................................16
4.1.2 Multiple Values ..........................................16
4.1.3 Binary Content ...........................................16
Dawson & Stenerson Standards Track [Page 2]RFC 2445 iCalendar November 1998
4.1.4 Character Set ............................................17
4.2 Property Parameters .........................................17
4.2.1 Alternate Text Representation ............................18
4.2.2 Common Name ..............................................19
4.2.3 Calendar User Type .......................................20
4.2.4 Delegators ...............................................20
4.2.5 Delegatees ...............................................21
4.2.6 Directory Entry Reference ................................21
4.2.7 Inline Encoding ..........................................22
4.2.8 Format Type ..............................................23
4.2.9 Free/Busy Time Type ......................................23
4.2.10 Language ................................................24
4.2.11 Group or List Membership ................................25
4.2.12 Participation Status ....................................25
4.2.13 Recurrence Identifier Range .............................27
4.2.14 Alarm Trigger Relationship ..............................27
4.2.15 Relationship Type .......................................28
4.2.16 Participation Role ......................................29
4.2.17 RSVP Expectation ........................................29
4.2.18 Sent By .................................................30
4.2.19 Time Zone Identifier ....................................30
4.2.20 Value Data Types ........................................32
4.3 Property Value Data Types ...................................32
4.3.1 Binary ...................................................33
4.3.2 Boolean ..................................................33
4.3.3 Calendar User Address ....................................34
4.3.4 Date .....................................................34
4.3.5 Date-Time ................................................35
4.3.6 Duration .................................................37
4.3.7 Float ....................................................38
4.3.8 Integer ..................................................38
4.3.9 Period of Time ...........................................39
4.3.10 Recurrence Rule .........................................40
4.3.11 Text ....................................................45
4.3.12 Time ....................................................47
4.3.13 URI .....................................................49
4.3.14 UTC Offset ..............................................49
4.4 iCalendar Object ............................................50
4.5 Property ....................................................51
4.6 Calendar Components .........................................51
4.6.1 Event Component ..........................................52
4.6.2 To-do Component ..........................................55
4.6.3 Journal Component ........................................56
4.6.4 Free/Busy Component ......................................58
4.6.5 Time Zone Component ......................................60
4.6.6 Alarm Component ..........................................67
4.7 Calendar Properties .........................................73
4.7.1 Calendar Scale ...........................................73
Dawson & Stenerson Standards Track [Page 3]RFC 2445 iCalendar November 1998
4.7.2 Method ...................................................74
4.7.3 Product Identifier .......................................75
4.7.4 Version ..................................................76
4.8 Component Properties ........................................77
4.8.1 Descriptive Component Properties .........................77
4.8.1.1 Attachment ...........................................77
4.8.1.2 Categories ...........................................78
4.8.1.3 Classification .......................................79
4.8.1.4 Comment ..............................................80
4.8.1.5 Description ..........................................81
4.8.1.6 Geographic Position ..................................82
4.8.1.7 Location .............................................84
4.8.1.8 Percent Complete .....................................85
4.8.1.9 Priority .............................................85
4.8.1.10 Resources ...........................................87
4.8.1.11 Status ..............................................88
4.8.1.12 Summary .............................................89
4.8.2 Date and Time Component Properties .......................90
4.8.2.1 Date/Time Completed ..................................90
4.8.2.2 Date/Time End ........................................91
4.8.2.3 Date/Time Due ........................................92
4.8.2.4 Date/Time Start ......................................93
4.8.2.5 Duration .............................................94
4.8.2.6 Free/Busy Time .......................................95
4.8.2.7 Time Transparency ....................................96
4.8.3 Time Zone Component Properties ...........................97
4.8.3.1 Time Zone Identifier .................................97
4.8.3.2 Time Zone Name .......................................98
4.8.3.3 Time Zone Offset From ................................99
4.8.3.4 Time Zone Offset To .................................100
4.8.3.5 Time Zone URL .......................................101
4.8.4 Relationship Component Properties .......................102
4.8.4.1 Attendee ............................................102
4.8.4.2 Contact .............................................104
4.8.4.3 Organizer ...........................................106
4.8.4.4 Recurrence ID .......................................107
4.8.4.5 Related To ..........................................109
4.8.4.6 Uniform Resource Locator ............................110
4.8.4.7 Unique Identifier ...................................111
4.8.5 Recurrence Component Properties .........................112
4.8.5.1 Exception Date/Times ................................112
4.8.5.2 Exception Rule ......................................114
4.8.5.3 Recurrence Date/Times ...............................115
4.8.5.4 Recurrence Rule .....................................117
4.8.6 Alarm Component Properties ..............................126
4.8.6.1 Action ..............................................126
4.8.6.2 Repeat Count ........................................126
4.8.6.3 Trigger .............................................127
Dawson & Stenerson Standards Track [Page 4]RFC 2445 iCalendar November 1998
4.8.7 Change Management Component Properties ..................129
4.8.7.1 Date/Time Created ...................................129
4.8.7.2 Date/Time Stamp .....................................130
4.8.7.3 Last Modified .......................................131
4.8.7.4 Sequence Number .....................................131
4.8.8 Miscellaneous Component Properties ......................133
4.8.8.1 Non-standard Properties .............................133
4.8.8.2 Request Status ......................................134
5 iCalendar Object Examples......................................136
6 Recommended Practices..........................................140
7 Registration of Content Type Elements..........................141
7.1 Registration of New and Modified iCalendar Object Methods ..141
7.2 Registration of New Properties .............................141
7.2.1 Define the property .....................................142
7.2.2 Post the Property definition ............................143
7.2.3 Allow a comment period ..................................143
7.2.4 Submit the property for approval ........................143
7.3 Property Change Control ....................................143
8 References.....................................................144
9 Acknowledgments................................................145
10 Authors' and Chairs' Addresses................................146
11 Full Copyright Statement......................................148
1 Introduction
The use of calendaring and scheduling has grown considerably in the
last decade. Enterprise and inter-enterprise business has become
dependent on rapid scheduling of events and actions using this
information technology. However, the longer term growth of
calendaring and scheduling, is currently limited by the lack of
Internet standards for the message content types that are central to
these knowledgeware applications. This memo is intended to progress
the level of interoperability possible between dissimilar calendaring
and scheduling applications. This memo defines a MIME content type
for exchanging electronic calendaring and scheduling information. The
Internet Calendaring and Scheduling Core Object Specification, or
iCalendar, allows for the capture and exchange of information
normally stored within a calendaring and scheduling application; such
as a Personal Information Manager (PIM) or a Group Scheduling
product.
The iCalendar format is suitable as an exchange format between
applications or systems. The format is defined in terms of a MIME
content type. This will enable the object to be exchanged using
several transports, including but not limited to SMTP, HTTP, a file
system, desktop interactive protocols such as the use of a memory-
based clipboard or drag/drop interactions, point-to-point
asynchronous communication, wired-network transport, or some form of
Dawson & Stenerson Standards Track [Page 5]RFC 2445 iCalendar November 1998
unwired transport such as infrared might also be used.
The memo also provides for the definition of iCalendar object methods
that will map this content type to a set of messages for supporting
calendaring and scheduling operations such as requesting, replying
to, modifying, and canceling meetings or appointments, to-dos and
journal entries. The iCalendar object methods can be used to define
other calendaring and scheduling operations such a requesting for and
replying with free/busy time data. Such a scheduling protocol is
defined in the iCalendar Transport-independent Interoperability
Protocol (iTIP) defined in [ITIP].
The memo also includes a formal grammar for the content type based on
the Internet ABNF defined in [RFC 2234]. This ABNF is required for
the implementation of parsers and to serve as the definitive
reference when ambiguities or questions arise in interpreting the
descriptive prose definition of the memo.
2 Basic Grammar and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY" and
"OPTIONAL" in this document are to be interoperated as described in
[RFC 2119].
This memo makes use of both a descriptive prose and a more formal
notation for defining the calendaring and scheduling format.
The notation used in this memo is the ABNF notation of [RFC 2234].
Readers intending on implementing this format defined in this memo
should be familiar with this notation in order to properly interpret
the specifications of this memo.
All numeric and hexadecimal values used in this memo are given in
decimal notation.
All names of properties, property parameters, enumerated property
values and property parameter values are case-insensitive. However,
all other property values are case-sensitive, unless otherwise
stated.
Note: All indented editorial notes, such as this one, are
intended to provide the reader with additional information. The
information is not essential to the building of an
implementation conformant with this memo. The information is
provided to highlight a particular feature or characteristic of
the memo.
Dawson & Stenerson Standards Track [Page 6]RFC 2445 iCalendar November 1998
The format for the iCalendar object is based on the syntax of the
[RFC 2425] content type. While the iCalendar object is not a profile
of the [RFC 2425] content type, it does reuse a number of the
elements from the [RFC 2425] specification.
2.1 Formatting Conventions
The mechanisms defined in this memo are defined in prose. Many of the
terms used to describe these have common usage that is different than
the standards usage of this memo. In order to reference within this
memo elements of the calendaring and scheduling model, core object
(this memo) or interoperability protocol [ITIP] some formatting
conventions have been used. Calendaring and scheduling roles are
referred to in quoted-strings of text with the first character of
each word in upper case. For example, "Organizer" refers to a role of
a "Calendar User" within the scheduling protocol defined by [ITIP].
Calendar components defined by this memo are referred to with
capitalized, quoted-strings of text. All calendar components start
with the letter "V". For example, "VEVENT" refers to the event
calendar component, "VTODO" refers to the to-do calendar component
and "VJOURNAL" refers to the daily journal calendar component.
Scheduling methods defined by [ITIP] are referred to with
capitalized, quoted-strings of text. For example, "REQUEST" refers to
the method for requesting a scheduling calendar component be created
or modified, "REPLY" refers to the method a recipient of a request
uses to update their status with the "Organizer" of the calendar
component.
The properties defined by this memo are referred to with capitalized,
quoted-strings of text, followed by the word "property". For example,
"ATTENDEE" property refers to the iCalendar property used to convey
the calendar address of a calendar user. Property parameters defined
by this memo are referred to with lowercase, quoted-strings of text,
followed by the word "parameter". For example, "value" parameter
refers to the iCalendar property parameter used to override the
default data type for a property value. Enumerated values defined by
this memo are referred to with capitalized text, either alone or
followed by the word "value". For example, the "MINUTELY" value can
be used with the "FREQ" component of the "RECUR" data type to specify
repeating components based on an interval of one minute or more.
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RFC 2445 iCalendar November 1998
2.2 Related Memos
Implementers will need to be familiar with several other memos that,
along with this memo, form a framework for Internet calendaring and
scheduling standards. This memo, [ICAL], specifies a core
specification of objects, data types, properties and property
parameters.
[ITIP] - specifies an interoperability protocol for scheduling
between different implementations;
[IMIP] specifies an Internet email binding for [ITIP].
This memo does not attempt to repeat the specification of concepts or
definitions from these other memos. Where possible, references are
made to the memo that provides for the specification of these
concepts or definitions.
2.3 International Considerations
In the rest of this document, descriptions of characters are of the
form "character name (codepoint)", where "codepoint" is from the US-
ASCII character set. The "character name" is the authoritative
description; (codepoint) is a reference to that character in US-ASCII
or US-ASCII compatible sets (for example the ISO-8859-x family, UTF-
8, ISO-2022-xx, KOI8-R). If a non-US-ASCII compatible character set
is used, appropriate code-point from that character set MUST be
chosen instead. Use of non-US-ASCII-compatible character sets is NOT
recommended.
3 Registration Information
The Calendaring and Scheduling Core Object Specification is intended
for use as a MIME content type. However, the implementation of the
memo is in no way limited solely as a MIME content type.
3.1 Content Type
The following text is intended to register this memo as the MIME
content type "text/calendar".
To: ietf-types@uninett.no
Subject: Registration of MIME content type text/calendar.
MIME media type name: text
MIME subtype name: calendar
Dawson & Stenerson Standards Track [Page 8]RFC 2445 iCalendar November 1998
3.2 Parameters
Required parameters: none
Optional parameters: charset, method, component and optinfo
The "charset" parameter is defined in [RFC 2046] for other body
parts. It is used to identify the default character set used within
the body part.
The "method" parameter is used to convey the iCalendar object method
or transaction semantics for the calendaring and scheduling
information. It also is an identifier for the restricted set of
properties and values that the iCalendar object consists of. The
parameter is to be used as a guide for applications interpreting the
information contained within the body part. It SHOULD NOT be used to
exclude or require particular pieces of information unless the
identified method definition specifically calls for this behavior.
Unless specifically forbidden by a particular method definition, a
text/calendar content type can contain any set of properties
permitted by the Calendaring and Scheduling Core Object
Specification. The "method" parameter MUST be the same value as that
specified in the "METHOD" component property in the iCalendar object.
If one is present, the other MUST also be present.
The value for the "method" parameter is defined as follows:
method = 1*(ALPHA / DIGIT / "-")
; IANA registered iCalendar object method
The "component" parameter conveys the type of iCalendar calendar
component within the body part. If the iCalendar object contains more
than one calendar component type, then multiple component parameters
MUST be specified.
The value for the "component" parameter is defined as follows:
component = ("VEVENT" / "VTODO" / "VJOURNAL" / "VFREEBUSY"
/ "VTIMEZONE" / x-name / iana-token)
The "optinfo" parameter conveys optional information about the
iCalendar object within the body part. This parameter can only
specify semantics already specified by the iCalendar object and that
can be otherwise determined by parsing the body part. In addition,
the optional information specified by this parameter MUST be
consistent with that information specified by the iCalendar object.
For example, it can be used to convey the "Attendee" response status
to a meeting request. The parameter value consists of a string value.
Dawson & Stenerson Standards Track [Page 9]RFC 2445 iCalendar November 1998
The parameter can be specified multiple times.
This parameter MAY only specify semantics already specified by the
iCalendar object and that can be otherwise determined by parsing the
body part.
The value for the "optinfo" parameter is defined as follows:
optinfo = infovalue / qinfovalue
infovalue = iana-token / x-name
qinfovalue = DQUOTE (infovalue) DQUOTE
3.3 Content Header Fields
Optional content header fields: Any header fields defined by [RFC
2045].
3.4 Encoding Considerations
This MIME content type can contain 8bit characters, so the use of
quoted-printable or BASE64 MIME content-transfer-encodings might be
necessary when iCalendar objects are transferred across protocols
restricted to the 7bit repertoire. Note that a text valued property
in the content entity can also have content encoding of special
characters using a BACKSLASH character (US-ASCII decimal 92)
escapement technique. This means that content values can end up
encoded twice.
3.5 Security Considerations
SPOOFING - - In this memo, the "Organizer" is the only person
authorized to make changes to an existing "VEVENT", "VTODO",
"VJOURNAL" calendar component and redistribute the updates to the
"Attendees". An iCalendar object that maliciously changes or cancels
an existing "VEVENT", "VTODO" or "VJOURNAL" or "VFREEBUSY" calendar
component might be constructed by someone other than the "Organizer"
and sent to the "Attendees". In addition in this memo, other than the
"Organizer", an "Attendee" of a "VEVENT", "VTODO", "VJOURNAL"
calendar component is the only other person authorized to update any
parameter associated with their "ATTENDEE" property and send it to
the "Organizer". An iCalendar object that maliciously changes the
"ATTENDEE" parameters can be constructed by someone other than the
real "Attendee" and sent to the "Organizer".
Dawson & Stenerson Standards Track [Page 10]RFC 2445 iCalendar November 1998
PROCEDURAL ALARMS - - An iCalendar object can be created that
contains a "VEVENT" and "VTODO" calendar component with "VALARM"
calendar components. The "VALARM" calendar component can be of type
PROCEDURE and can have an attachment containing some sort of
executable program. Implementations that incorporate these types of
alarms are subject to any virus or malicious attack that might occur
as a result of executing the attachment.
ATTACHMENTS - - An iCalendar object can include references to Uniform
Resource Locators that can be programmed resources.
Implementers and users of this memo should be aware of the network
security implications of accepting and parsing such information. In
addition, the security considerations observed by implementations of
electronic mail systems should be followed for this memo.
3.6 Interoperability Considerations
This MIME content type is intended to define a common format for
conveying calendaring and scheduling information between different
systems. It is heavily based on the earlier [VCAL] industry
specification.
3.7 Applications Which Use This Media Type
This content-type is designed for widespread use by Internet
calendaring and scheduling applications. In addition, applications in
the workflow and document management area might find this content-
type applicable. The [ITIP] and [IMIP] Internet protocols directly
use this content-type also. Future work on an Internet calendar
access protocol will utilize this content-type too.
3.8 Additional Information
This memo defines this content-type.
3.9 Magic Numbers
None.
3.10 File Extensions
The file extension of "ics" is to be used to designate a file
containing (an arbitrary set of) calendaring and scheduling
information consistent with this MIME content type.
Dawson & Stenerson Standards Track [Page 11]
RFC 2445 iCalendar November 1998
The file extension of "ifb" is to be used to designate a file
containing free or busy time information consistent with this MIME
content type.
Macintosh file type codes: The file type code of "iCal" is to be used
in Apple MacIntosh operating system environments to designate a file
containing calendaring and scheduling information consistent with
this MIME media type.
The file type code of "iFBf" is to be used in Apple MacIntosh
operating system environments to designate a file containing free or
busy time information consistent with this MIME media type.
3.11 Contact for Further Information:
Frank Dawson
6544 Battleford Drive
Raleigh, NC 27613-3502
919-676-9515 (Telephone)
919-676-9564 (Data/Facsimile)
Frank_Dawson@Lotus.com (Internet Mail)
Derik Stenerson
One Microsoft Way
Redmond, WA 98052-6399
425-936-5522 (Telephone)
425-936-7329 (Facsimile)
deriks@microsoft.com (Internet Mail)
3.12 Intended Usage
COMMON
3.13 Authors/Change Controllers
Frank Dawson
6544 Battleford Drive
Raleigh, NC 27613-3502
919-676-9515 (Telephone)
919-676-9564 (Data/Facsimile)
Frank_Dawson@Lotus.com (Internet Mail)
Derik Stenerson
One Microsoft Way
Redmond, WA 98052-6399
425-936-5522 (Telephone)
425-936-7329 (Facsimile)
deriks@microsoft.com (Internet Mail)
Dawson & Stenerson Standards Track [Page 12]
RFC 2445 iCalendar November 1998
4 iCalendar Object Specification
The following sections define the details of a Calendaring and
Scheduling Core Object Specification. This information is intended to
be an integral part of the MIME content type registration. In
addition, this information can be used independent of such content
registration. In particular, this memo has direct applicability for
use as a calendaring and scheduling exchange format in file-, memory-
or network-based transport mechanisms.
4.1 Content Lines
The iCalendar object is organized into individual lines of text,
called content lines. Content lines are delimited by a line break,
which is a CRLF sequence (US-ASCII decimal 13, followed by US-ASCII
decimal 10).
Lines of text SHOULD NOT be longer than 75 octets, excluding the line
break. Long content lines SHOULD be split into a multiple line
representations using a line "folding" technique. That is, a long
line can be split between any two characters by inserting a CRLF
immediately followed by a single linear white space character (i.e.,
SPACE, US-ASCII decimal 32 or HTAB, US-ASCII decimal 9). Any sequence
of CRLF followed immediately by a single linear white space character
is ignored (i.e., removed) when processing the content type.
For example the line:
DESCRIPTION:This is a long description that exists on a long line.
Can be represented as:
DESCRIPTION:This is a lo
ng description
that exists on a long line.
The process of moving from this folded multiple line representation
to its single line representation is called "unfolding". Unfolding is
accomplished by removing the CRLF character and the linear white
space character that immediately follows.
When parsing a content line, folded lines MUST first be unfolded
according to the unfolding procedure described above. When generating
a content line, lines longer than 75 octets SHOULD be folded
according to the folding procedure described above.
Dawson & Stenerson Standards Track [Page 13]RFC 2445 iCalendar November 1998
The content information associated with an iCalendar object is
formatted using a syntax similar to that defined by [RFC 2425]. That
is, the content information consists of CRLF-separated content lines.
The following notation defines the lines of content in an iCalendar
object:
contentline = name *(";" param ) ":" value CRLF
; This ABNF is just a general definition for an initial parsing
; of the content line into its property name, parameter list,
; and value string
; When parsing a content line, folded lines MUST first
; be unfolded according to the unfolding procedure
; described above. When generating a content line, lines
; longer than 75 octets SHOULD be folded according to
; the folding procedure described above.
name = x-name / iana-token
iana-token = 1*(ALPHA / DIGIT / "-")
; iCalendar identifier registered with IANA
x-name = "X-" [vendorid "-"] 1*(ALPHA / DIGIT / "-")
; Reservered for experimental use. Not intended for use in
; released products.
vendorid = 3*(ALPHA / DIGIT) ;Vendor identification
param = param-name "=" param-value
*("," param-value)
; Each property defines the specific ABNF for the parameters
; allowed on the property. Refer to specific properties for
; precise parameter ABNF.
param-name = iana-token / x-token
param-value = paramtext / quoted-string
paramtext = *SAFE-CHAR
value = *VALUE-CHAR
quoted-string = DQUOTE *QSAFE-CHAR DQUOTE
NON-US-ASCII = %x80-F8
; Use restricted by charset parameter
; on outer MIME object (UTF-8 preferred)
Dawson & Stenerson Standards Track [Page 14]RFC 2445 iCalendar November 1998
QSAFE-CHAR = WSP / %x21 / %x23-7E / NON-US-ASCII
; Any character except CTLs and DQUOTE
SAFE-CHAR = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E
/ NON-US-ASCII
; Any character except CTLs, DQUOTE, ";", ":", ","
VALUE-CHAR = WSP / %x21-7E / NON-US-ASCII
; Any textual character
CR = %x0D
; carriage return
LF = %x0A
; line feed
CRLF = CR LF
; Internet standard newline
CTL = %x00-08 / %x0A-1F / %x7F
; Controls
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
DIGIT = %x30-39
; 0-9
DQUOTE = %x22
; Quotation Mark
WSP = SPACE / HTAB
SPACE = %x20
HTAB = %x09
The property value component of a content line has a format that is
property specific. Refer to the section describing each property for
a definition of this format.
All names of properties, property parameters, enumerated property
values and property parameter values are case-insensitive. However,
all other property values are case-sensitive, unless otherwise
stated.
Dawson & Stenerson Standards Track [Page 15]RFC 2445 iCalendar November 1998
4.1.1 List and Field Separators
Some properties and parameters allow a list of values. Values in a
list of values MUST be separated by a COMMA character (US-ASCII
decimal 44). There is no significance to the order of values in a
list. For those parameter values (such as those that specify URI
values) that are specified in quoted-strings, the individual quoted-
strings are separated by a COMMA character (US-ASCII decimal 44).
Some property values are defined in terms of multiple parts. These
structured property values MUST have their value parts separated by a
SEMICOLON character (US-ASCII decimal 59).
Some properties allow a list of parameters. Each property parameter
in a list of property parameters MUST be separated by a SEMICOLON
character (US-ASCII decimal 59).
Property parameters with values containing a COLON, a SEMICOLON or a
COMMA character MUST be placed in quoted text.
For example, in the following properties a SEMICOLON is used to
separate property parameters from each other, and a COMMA is used to
separate property values in a value list.
ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT:MAILTO:
jsmith@host.com
RDATE;VALUE=DATE:19970304,19970504,19970704,19970904
4.1.2 Multiple Values
Some properties defined in the iCalendar object can have multiple
values. The general rule for encoding multi-valued items is to simply
create a new content line for each value, including the property
name. However, it should be noted that some properties support
encoding multiple values in a single property by separating the
values with a COMMA character (US-ASCII decimal 44). Individual
property definitions should be consulted for determining whether a
specific property allows multiple values and in which of these two
forms.
4.1.3 Binary Content
Binary content information in an iCalendar object SHOULD be
referenced using a URI within a property value. That is the binary
content information SHOULD be placed in an external MIME entity that
can be referenced by a URI from within the iCalendar object. In
applications where this is not feasible, binary content information
Dawson & Stenerson Standards Track [Page 16]RFC 2445 iCalendar November 1998
can be included within an iCalendar object, but only after first
encoding it into text using the "BASE64" encoding method defined in
[RFC 2045]. Inline binary contact SHOULD only be used in applications
whose special circumstances demand that an iCalendar object be
expressed as a single entity. A property containing inline binary
content information MUST specify the "ENCODING" property parameter.
Binary content information placed external to the iCalendar object
MUST be referenced by a uniform resource identifier (URI).
The following example specifies an "ATTACH" property that references
an attachment external to the iCalendar object with a URI reference:
ATTACH:http://xyz.com/public/quarterly-report.doc
The following example specifies an "ATTACH" property with inline
binary encoded content information:
ATTACH;FMTTYPE=image/basic;ENCODING=BASE64;VALUE=BINARY:
MIICajCCAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1U
EBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIE
<...remainder of "BASE64" encoded binary data...>
4.1.4 Character Set
There is not a property parameter to declare the character set used
in a property value. The default character set for an iCalendar
object is UTF-8 as defined in [RFC 2279].
The "charset" Content-Type parameter can be used in MIME transports
to specify any other IANA registered character set.
4.2 Property Parameters
A property can have attributes associated with it. These "property
parameters" contain meta-information about the property or the
property value. Property parameters are provided to specify such
information as the location of an alternate text representation for a
property value, the language of a text property value, the data type
of the property value and other attributes.
Property parameter values that contain the COLON (US-ASCII decimal
58), SEMICOLON (US-ASCII decimal 59) or COMMA (US-ASCII decimal 44)
character separators MUST be specified as quoted-string text values.
Property parameter values MUST NOT contain the DOUBLE-QUOTE (US-ASCII
decimal 22) character. The DOUBLE-QUOTE (US-ASCII decimal 22)
character is used as a delimiter for parameter values that contain
restricted characters or URI text. For example:
Dawson & Stenerson Standards Track [Page 17]RFC 2445 iCalendar November 1998
DESCRIPTION;ALTREP="http://www.wiz.org":The Fall'98 Wild Wizards
Conference - - Las Vegas, NV, USA
Property parameter values that are not in quoted strings are case
insensitive.
The general property parameters defined by this memo are defined by
the following notation:
parameter = altrepparam ; Alternate text representation
/ cnparam ; Common name
/ cutypeparam ; Calendar user type
/ delfromparam ; Delegator
/ deltoparam ; Delegatee
/ dirparam ; Directory entry
/ encodingparam ; Inline encoding
/ fmttypeparam ; Format type
/ fbtypeparam ; Free/busy time type
/ languageparam ; Language for text
/ memberparam ; Group or list membership
/ partstatparam ; Participation status
/ rangeparam ; Recurrence identifier range
/ trigrelparam ; Alarm trigger relationship
/ reltypeparam ; Relationship type
/ roleparam ; Participation role
/ rsvpparam ; RSVP expectation
/ sentbyparam ; Sent by
/ tzidparam ; Reference to time zone object
/ valuetypeparam ; Property value data type
/ ianaparam
; Some other IANA registered iCalendar parameter.
/ xparam
; A non-standard, experimental parameter.
ianaparam = iana-token "=" param-value *("," param-value)
xparam =x-name "=" param-value *("," param-value)
4.2.1 Alternate Text Representation
Parameter Name: ALTREP
Purpose: To specify an alternate text representation for the property
value.
Format Definition: The property parameter is defined by the following
notation:
Dawson & Stenerson Standards Track [Page 18]RFC 2445 iCalendar November 1998
altrepparam = "ALTREP" "=" DQUOTE uri DQUOTE
Description: The parameter specifies a URI that points to an
alternate representation for a textual property value. A property
specifying this parameter MUST also include a value that reflects the
default representation of the text value. The individual URI
parameter values MUST each be specified in a quoted-string.
Example:
DESCRIPTION;ALTREP="CID:<part3.msg.970415T083000@host.com>":Project
XYZ Review Meeting will include the following agenda items: (a)
Market Overview, (b) Finances, (c) Project Management
The "ALTREP" property parameter value might point to a "text/html"
content portion.
Content-Type:text/html
Content-Id:<part3.msg.970415T083000@host.com>
<html><body>
<p><b>Project XYZ Review Meeting</b> will include the following
agenda items:<ol><li>Market
Overview</li><li>Finances</li><li>Project Management</li></ol></p>
</body></html>
4.2.2 Common Name
Parameter Name: CN
Purpose: To specify the common name to be associated with the
calendar user specified by the property.
Format Definition: The property parameter is defined by the following
notation:
cnparam = "CN" "=" param-value
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies the common name to be
associated with the calendar user specified by the property. The
parameter value is text. The parameter value can be used for display
text to be associated with the calendar address specified by the
property.
Dawson & Stenerson Standards Track [Page 19]RFC 2445 iCalendar November 1998
Example:
ORGANIZER;CN="John Smith":MAILTO:jsmith@host.com
4.2.3 Calendar User Type
Parameter Name: CUTYPE
Purpose: To specify the type of calendar user specified by the
property.
Format Definition: The property parameter is defined by the following
notation:
cutypeparam = "CUTYPE" "="
("INDIVIDUAL" ; An individual
/ "GROUP" ; A group of individuals
/ "RESOURCE" ; A physical resource
/ "ROOM" ; A room resource
/ "UNKNOWN" ; Otherwise not known
/ x-name ; Experimental type
/ iana-token) ; Other IANA registered
; type
; Default is INDIVIDUAL
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the type of calendar
user specified by the property. If not specified on a property that
allows this parameter, the default is INDIVIDUAL.
Example:
ATTENDEE;CUTYPE=GROUP:MAILTO:ietf-calsch@imc.org
4.2.4 Delegators
Parameter Name: DELEGATED-FROM
Purpose: To specify the calendar users that have delegated their
participation to the calendar user specified by the property.
Format Definition: The property parameter is defined by the following
notation:
delfromparam = "DELEGATED-FROM" "=" DQUOTE cal-address DQUOTE
*("," DQUOTE cal-address DQUOTE)
Dawson & Stenerson Standards Track [Page 20]RFC 2445 iCalendar November 1998
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. This parameter can be specified on a property
that has a value type of calendar address. This parameter specifies
those calendar uses that have delegated their participation in a
group scheduled event or to-do to the calendar user specified by the
property. The value MUST be a MAILTO URI as defined in [RFC 1738].
The individual calendar address parameter values MUST each be
specified in a quoted-string.
Example:
ATTENDEE;DELEGATED-FROM="MAILTO:jsmith@host.com":MAILTO:
jdoe@host.com
4.2.5 Delegatees
Parameter Name: DELEGATED-TO
Purpose: To specify the calendar users to whom the calendar user
specified by the property has delegated participation.
Format Definition: The property parameter is defined by the following
notation:
deltoparam = "DELEGATED-TO" "=" DQUOTE cal-address DQUOTE
*("," DQUOTE cal-address DQUOTE)
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. This parameter specifies those calendar users
whom have been delegated participation in a group scheduled event or
to-do by the calendar user specified by the property. The value MUST
be a MAILTO URI as defined in [RFC 1738]. The individual calendar
address parameter values MUST each be specified in a quoted-string.
Example:
ATTENDEE;DELEGATED-TO="MAILTO:jdoe@host.com","MAILTO:jqpublic@
host.com":MAILTO:jsmith@host.com
4.2.6 Directory Entry Reference
Parameter Name: DIR
Purpose: To specify reference to a directory entry associated with
the calendar user specified by the property.
Format Definition: The property parameter is defined by the following
notation:
Dawson & Stenerson Standards Track [Page 21]RFC 2445 iCalendar November 1998
dirparam = "DIR" "=" DQUOTE uri DQUOTE
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies a reference to the
directory entry associated with the calendar user specified by the
property. The parameter value is a URI. The individual URI parameter
values MUST each be specified in a quoted-string.
Example:
ORGANIZER;DIR="ldap://host.com:6666/o=eDABC%20Industries,c=3DUS??
(cn=3DBJim%20Dolittle)":MAILTO:jimdo@host1.com
4.2.7 Inline Encoding
Parameter Name: ENCODING
Purpose: To specify an alternate inline encoding for the property
value.
Format Definition: The property parameter is defined by the following
notation:
encodingparam = "ENCODING" "="
("8BIT"
; "8bit" text encoding is defined in [RFC 2045]
/ "BASE64"
; "BASE64" binary encoding format is defined in [RFC 2045]
/ iana-token
; Some other IANA registered iCalendar encoding type
/ x-name)
; A non-standard, experimental encoding type
Description: The property parameter identifies the inline encoding
used in a property value. The default encoding is "8BIT",
corresponding to a property value consisting of text. The "BASE64"
encoding type corresponds to a property value encoded using the
"BASE64" encoding defined in [RFC 2045].
If the value type parameter is ";VALUE=BINARY", then the inline
encoding parameter MUST be specified with the value
";ENCODING=BASE64".
Dawson & Stenerson Standards Track [Page 22]RFC 2445 iCalendar November 1998
Example:
ATTACH;FMTYPE=IMAGE/JPEG;ENCODING=BASE64;VALUE=BINARY:MIICajC
CAdOgAwIBAgICBEUwDQYJKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDA
qBgNVBAoTI05ldHNjYXBlIENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRw
<...remainder of "BASE64" encoded binary data...>
4.2.8 Format Type
Parameter Name: FMTTYPE
Purpose: To specify the content type of a referenced object.
Format Definition: The property parameter is defined by the following
notation:
fmttypeparam = "FMTTYPE" "=" iana-token
; A IANA registered content type
/ x-name
; A non-standard content type
Description: This parameter can be specified on properties that are
used to reference an object. The parameter specifies the content type
of the referenced object. For example, on the "ATTACH" property, a
FTP type URI value does not, by itself, necessarily convey the type
of content associated with the resource. The parameter value MUST be
the TEXT for either an IANA registered content type or a non-standard
content type.
Example:
ATTACH;FMTTYPE=application/binary:ftp://domain.com/pub/docs/
agenda.doc
4.2.9 Free/Busy Time Type
Parameter Name: FBTYPE
Purpose: To specify the free or busy time type.
Format Definition: The property parameter is defined by the following
notation:
fbtypeparam = "FBTYPE" "=" ("FREE" / "BUSY"
/ "BUSY-UNAVAILABLE" / "BUSY-TENTATIVE"
/ x-name
; Some experimental iCalendar data type.
/ iana-token)
Dawson & Stenerson Standards Track [Page 23]RFC 2445 iCalendar November 1998
; Some other IANA registered iCalendar data type.
Description: The parameter specifies the free or busy time type. The
value FREE indicates that the time interval is free for scheduling.
The value BUSY indicates that the time interval is busy because one
or more events have been scheduled for that interval. The value
BUSY-UNAVAILABLE indicates that the time interval is busy and that
the interval can not be scheduled. The value BUSY-TENTATIVE indicates
that the time interval is busy because one or more events have been
tentatively scheduled for that interval. If not specified on a
property that allows this parameter, the default is BUSY.
Example: The following is an example of this parameter on a FREEBUSY
property.
FREEBUSY;FBTYPE=BUSY:19980415T133000Z/19980415T170000Z
4.2.10 Language
Parameter Name: LANGUAGE
Purpose: To specify the language for text values in a property or
property parameter.
Format Definition: The property parameter is defined by the following
notation:
languageparam = "LANGUAGE" "=" language
language = <Text identifying a language, as defined in [RFC 1766]>
Description: This parameter can be specified on properties with a
text value type. The parameter identifies the language of the text in
the property or property parameter value. The value of the "language"
property parameter is that defined in [RFC 1766].
For transport in a MIME entity, the Content-Language header field can
be used to set the default language for the entire body part.
Otherwise, no default language is assumed.
Example:
SUMMARY;LANGUAGE=us-EN:Company Holiday Party
LOCATION;LANGUAGE=en:Germany
LOCATION;LANGUAGE=no:Tyskland
Dawson & Stenerson Standards Track [Page 24]RFC 2445 iCalendar November 1998
The following example makes use of the Quoted-Printable encoding in
order to represent non-ASCII characters.
LOCATION;LANGUAGE=da:K=F8benhavn
LOCATION;LANGUAGE=en:Copenhagen
4.2.11 Group or List Membership
Parameter Name: MEMBER
Purpose: To specify the group or list membership of the calendar user
specified by the property.
Format Definition: The property parameter is defined by the following
notation:
memberparam = "MEMBER" "=" DQUOTE cal-address DQUOTE
*("," DQUOTE cal-address DQUOTE)
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the groups or list
membership for the calendar user specified by the property. The
parameter value either a single calendar address in a quoted-string
or a COMMA character (US-ASCII decimal 44) list of calendar
addresses, each in a quoted-string. The individual calendar address
parameter values MUST each be specified in a quoted-string.
Example:
ATTENDEE;MEMBER="MAILTO:ietf-calsch@imc.org":MAILTO:jsmith@host.com
ATTENDEE;MEMBER="MAILTO:projectA@host.com","MAILTO:projectB@host.
com":MAILTO:janedoe@host.com
4.2.12 Participation Status
Parameter Name: PARTSTAT
Purpose: To specify the participation status for the calendar user
specified by the property.
Format Definition: The property parameter is defined by the following
notation:
partstatparam = "PARTSTAT" "="
("NEEDS-ACTION" ; Event needs action
/ "ACCEPTED" ; Event accepted
/ "DECLINED" ; Event declined
Dawson & Stenerson Standards Track [Page 25]RFC 2445 iCalendar November 1998
/ "TENTATIVE" ; Event tentatively
; accepted
/ "DELEGATED" ; Event delegated
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered
; status
; These are the participation statuses for a "VEVENT". Default is
; NEEDS-ACTION
partstatparam /= "PARTSTAT" "="
("NEEDS-ACTION" ; To-do needs action
/ "ACCEPTED" ; To-do accepted
/ "DECLINED" ; To-do declined
/ "TENTATIVE" ; To-do tentatively
; accepted
/ "DELEGATED" ; To-do delegated
/ "COMPLETED" ; To-do completed.
; COMPLETED property has
;date/time completed.
/ "IN-PROCESS" ; To-do in process of
; being completed
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered
; status
; These are the participation statuses for a "VTODO". Default is
; NEEDS-ACTION
partstatparam /= "PARTSTAT" "="
("NEEDS-ACTION" ; Journal needs action
/ "ACCEPTED" ; Journal accepted
/ "DECLINED" ; Journal declined
/ x-name ; Experimental status
/ iana-token) ; Other IANA registered
; status
; These are the participation statuses for a "VJOURNAL". Default is
; NEEDS-ACTION
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the participation
status for the calendar user specified by the property value. The
parameter values differ depending on whether they are associated with
a group scheduled "VEVENT", "VTODO" or "VJOURNAL". The values MUST
match one of the values allowed for the given calendar component. If
not specified on a property that allows this parameter, the default
value is NEEDS-ACTION.
Example:
ATTENDEE;PARTSTAT=DECLINED:MAILTO:jsmith@host.com
Dawson & Stenerson Standards Track [Page 26]RFC 2445 iCalendar November 1998
4.2.13 Recurrence Identifier Range
Parameter Name: RANGE
Purpose: To specify the effective range of recurrence instances from
the instance specified by the recurrence identifier specified by the
property.
Format Definition: The property parameter is defined by the following
notation:
rangeparam = "RANGE" "=" ("THISANDPRIOR"
; To specify all instances prior to the recurrence identifier
/ "THISANDFUTURE")
; To specify the instance specified by the recurrence identifier
; and all subsequent recurrence instances
Description: The parameter can be specified on a property that
specifies a recurrence identifier. The parameter specifies the
effective range of recurrence instances that is specified by the
property. The effective range is from the recurrence identified
specified by the property. If this parameter is not specified an
allowed property, then the default range is the single instance
specified by the recurrence identifier value of the property. The
parameter value can be "THISANDPRIOR" to indicate a range defined by
the recurrence identified value of the property and all prior
instances. The parameter value can also be "THISANDFUTURE" to
indicate a range defined by the recurrence identifier and all
subsequent instances.
Example:
RECURRENCE-ID;RANGE=THISANDPRIOR:19980401T133000Z
4.2.14 Alarm Trigger Relationship
Parameter Name: RELATED
Purpose: To specify the relationship of the alarm trigger with
respect to the start or end of the calendar component.
Format Definition: The property parameter is defined by the following
notation:
trigrelparam = "RELATED" "="
("START" ; Trigger off of start
/ "END") ; Trigger off of end
Dawson & Stenerson Standards Track [Page 27]RFC 2445 iCalendar November 1998
Description: The parameter can be specified on properties that
specify an alarm trigger with a DURATION value type. The parameter
specifies whether the alarm will trigger relative to the start or end
of the calendar component. The parameter value START will set the
alarm to trigger off the start of the calendar component; the
parameter value END will set the alarm to trigger off the end of the
calendar component. If the parameter is not specified on an allowable
property, then the default is START.
Example:
TRIGGER;RELATED=END:PT5M
4.2.15 Relationship Type
Parameter Name: RELTYPE
Purpose: To specify the type of hierarchical relationship associated
with the calendar component specified by the property.
Format Definition: The property parameter is defined by the following
notation:
reltypeparam = "RELTYPE" "="
("PARENT" ; Parent relationship. Default.
/ "CHILD" ; Child relationship
/ "SIBLING ; Sibling relationship
/ iana-token ; Some other IANA registered
; iCalendar relationship type
/ x-name) ; A non-standard, experimental
; relationship type
Description: This parameter can be specified on a property that
references another related calendar. The parameter specifies the
hierarchical relationship type of the calendar component referenced
by the property. The parameter value can be PARENT, to indicate that
the referenced calendar component is a superior of calendar
component; CHILD to indicate that the referenced calendar component
is a subordinate of the calendar component; SIBLING to indicate that
the referenced calendar component is a peer of the calendar
component. If this parameter is not specified on an allowable
property, the default relationship type is PARENT.
Example:
RELATED-TO;RELTYPE=SIBLING:<19960401-080045-4000F192713@host.com>
Dawson & Stenerson Standards Track [Page 28]RFC 2445 iCalendar November 1998
4.2.16 Participation Role
Parameter Name: ROLE
Purpose: To specify the participation role for the calendar user
specified by the property.
Format Definition: The property parameter is defined by the following
notation:
roleparam = "ROLE" "="
("CHAIR" ; Indicates chair of the
; calendar entity
/ "REQ-PARTICIPANT" ; Indicates a participant whose
; participation is required
/ "OPT-PARTICIPANT" ; Indicates a participant whose
; participation is optional
/ "NON-PARTICIPANT" ; Indicates a participant who is
; copied for information
; purposes only
/ x-name ; Experimental role
/ iana-token) ; Other IANA role
; Default is REQ-PARTICIPANT
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies the participation
role for the calendar user specified by the property in the group
schedule calendar component. If not specified on a property that
allows this parameter, the default value is REQ-PARTICIPANT.
Example:
ATTENDEE;ROLE=CHAIR:MAILTO:mrbig@host.com
4.2.17 RSVP Expectation
Parameter Name: RSVP
Purpose: To specify whether there is an expectation of a favor of a
reply from the calendar user specified by the property value.
Format Definition: The property parameter is defined by the following
notation:
rsvpparam = "RSVP" "=" ("TRUE" / "FALSE")
; Default is FALSE
Dawson & Stenerson Standards Track [Page 29]RFC 2445 iCalendar November 1998
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter identifies the expectation of a
reply from the calendar user specified by the property value. This
parameter is used by the "Organizer" to request a participation
status reply from an "Attendee" of a group scheduled event or to-do.
If not specified on a property that allows this parameter, the
default value is FALSE.
Example:
ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host.com
4.2.18 Sent By
Parameter Name: SENT-BY
Purpose: To specify the calendar user that is acting on behalf of the
calendar user specified by the property.
Format Definition: The property parameter is defined by the following
notation:
sentbyparam = "SENT-BY" "=" DQUOTE cal-address DQUOTE
Description: This parameter can be specified on properties with a
CAL-ADDRESS value type. The parameter specifies the calendar user
that is acting on behalf of the calendar user specified by the
property. The parameter value MUST be a MAILTO URI as defined in [RFC
1738]. The individual calendar address parameter values MUST each be
specified in a quoted-string.
Example:
ORGANIZER;SENT-BY:"MAILTO:sray@host.com":MAILTO:jsmith@host.com
4.2.19 Time Zone Identifier
Parameter Name: TZID
Purpose: To specify the identifier for the time zone definition for a
time component in the property value.
Format Definition: This property parameter is defined by the
following notation:
tzidparam = "TZID" "=" [tzidprefix] paramtext CRLF
tzidprefix = "/"
Dawson & Stenerson Standards Track [Page 30]RFC 2445 iCalendar November 1998
Description: The parameter MUST be specified on the "DTSTART",
"DTEND", "DUE", "EXDATE" and "RDATE" properties when either a DATE-
TIME or TIME value type is specified and when the value is not either
a UTC or a "floating" time. Refer to the DATE-TIME or TIME value type
definition for a description of UTC and "floating time" formats. This
property parameter specifies a text value which uniquely identifies
the "VTIMEZONE" calendar component to be used when evaluating the
time portion of the property. The value of the TZID property
parameter will be equal to the value of the TZID property for the
matching time zone definition. An individual "VTIMEZONE" calendar
component MUST be specified for each unique "TZID" parameter value
specified in the iCalendar object.
The parameter MUST be specified on properties with a DATE-TIME value
if the DATE-TIME is not either a UTC or a "floating" time.
The presence of the SOLIDUS character (US-ASCII decimal 47) as a
prefix, indicates that this TZID represents a unique ID in a globally
defined time zone registry (when such registry is defined).
Note: This document does not define a naming convention for time
zone identifiers. Implementers may want to use the naming
conventions defined in existing time zone specifications such as
the public-domain Olson database [TZ]. The specification of
globally unique time zone identifiers is not addressed by this
document and is left for future study.
The following are examples of this property parameter:
DTSTART;TZID=US-Eastern:19980119T020000
DTEND;TZID=US-Eastern:19980119T030000
The TZID property parameter MUST NOT be applied to DATE-TIME or TIME
properties whose time values are specified in UTC.
The use of local time in a DATE-TIME or TIME value without the TZID
property parameter is to be interpreted as a local time value,
regardless of the existence of "VTIMEZONE" calendar components in the
iCalendar object.
For more information see the sections on the data types DATE-TIME and
TIME.
Dawson & Stenerson Standards Track [Page 31]RFC 2445 iCalendar November 1998
4.2.20 Value Data Types
Parameter Name: VALUE
Purpose: To explicitly specify the data type format for a property
value.
Format Definition: The "VALUE" property parameter is defined by the
following notation:
valuetypeparam = "VALUE" "=" valuetype
valuetype = ("BINARY"
/ "BOOLEAN"
/ "CAL-ADDRESS"
/ "DATE"
/ "DATE-TIME"
/ "DURATION"
/ "FLOAT"
/ "INTEGER"
/ "PERIOD"
/ "RECUR"
/ "TEXT"
/ "TIME"
/ "URI"
/ "UTC-OFFSET"
/ x-name
; Some experimental iCalendar data type.
/ iana-token)
; Some other IANA registered iCalendar data type.
Description: The parameter specifies the data type and format of the
property value. The property values MUST be of a single value type.
For example, a "RDATE" property cannot have a combination of DATE-
TIME and TIME value types.
If the property's value is the default value type, then this
parameter need not be specified. However, if the property's default
value type is overridden by some other allowable value type, then
this parameter MUST be specified.
4.3 Property Value Data Types
The properties in an iCalendar object are strongly typed. The
definition of each property restricts the value to be one of the
value data types, or simply value types, defined in this section. The
value type for a property will either be specified implicitly as the
default value type or will be explicitly specified with the "VALUE"
Dawson & Stenerson Standards Track [Page 32]RFC 2445 iCalendar November 1998
parameter. If the value type of a property is one of the alternate
valid types, then it MUST be explicitly specified with the "VALUE"
parameter.
4.3.1 Binary
Value Name: BINARY
Purpose: This value type is used to identify properties that contain
a character encoding of inline binary data. For example, an inline
attachment of an object code might be included in an iCalendar
object.
Formal Definition: The value type is defined by the following
notation:
binary = *(4b-char) [b-end]
; A "BASE64" encoded character string, as defined by [RFC 2045].
b-end = (2b-char "==") / (3b-char "=")
b-char = ALPHA / DIGIT / "+" / "/"
Description: Property values with this value type MUST also include
the inline encoding parameter sequence of ";ENCODING=BASE64". That
is, all inline binary data MUST first be character encoded using the
"BASE64" encoding method defined in [RFC 2045]. No additional content
value encoding (i.e., BACKSLASH character encoding) is defined for
this value type.
Example: The following is an abridged example of a "BASE64" encoded
binary value data.
ATTACH;VALUE=BINARY;ENCODING=BASE64:MIICajCCAdOgAwIBAgICBEUwDQY
JKoZIhvcNAQEEBQAwdzELMAkGA1UEBhMCVVMxLDAqBgNVBAoTI05ldHNjYXBlI
ENvbW11bmljYXRpb25zIENvcnBvcmF0aW9uMRwwGgYDVQQLExNJbmZv
<...remainder of "BASE64" encoded binary data...>
4.3.2 Boolean
Value Name: BOOLEAN
Purpose: This value type is used to identify properties that contain
either a "TRUE" or "FALSE" Boolean value.
Formal Definition: The value type is defined by the following
notation:
Dawson & Stenerson Standards Track [Page 33]RFC 2445 iCalendar November 1998
boolean = "TRUE" / "FALSE"
Description: These values are case insensitive text. No additional
content value encoding (i.e., BACKSLASH character encoding) is
defined for this value type.
Example: The following is an example of a hypothetical property that
has a BOOLEAN value type:
GIBBERISH:TRUE
4.3.3 Calendar User Address
Value Name: CAL-ADDRESS
Purpose: This value type is used to identify properties that contain
a calendar user address.
Formal Definition: The value type is as defined by the following
notation:
cal-address = uri
Description: The value is a URI as defined by [RFC 1738] or any other
IANA registered form for a URI. When used to address an Internet
email transport address for a calendar user, the value MUST be a
MAILTO URI, as defined by [RFC 1738]. No additional content value
encoding (i.e., BACKSLASH character encoding) is defined for this
value type.
Example:
ATTENDEE:MAILTO:jane_doe@host.com
4.3.4 Date
Value Name: DATE
Purpose: This value type is used to identify values that contain a
calendar date.
Formal Definition: The value type is defined by the following
notation:
date = date-value
date-value = date-fullyear date-month date-mday
date-fullyear = 4DIGIT
Dawson & Stenerson Standards Track [Page 34]RFC 2445 iCalendar November 1998
date-month = 2DIGIT ;01-12
date-mday = 2DIGIT ;01-28, 01-29, 01-30, 01-31
;based on month/year
Description: If the property permits, multiple "date" values are
specified as a COMMA character (US-ASCII decimal 44) separated list
of values. The format for the value type is expressed as the [ISO
8601] complete representation, basic format for a calendar date. The
textual format specifies a four-digit year, two-digit month, and
two-digit day of the month. There are no separator characters between
the year, month and day component text.
No additional content value encoding (i.e., BACKSLASH character
encoding) is defined for this value type.
Example: The following represents July 14, 1997:
19970714
4.3.5 Date-Time
Value Name: DATE-TIME
Purpose: This value type is used to identify values that specify a
precise calendar date and time of day.
Formal Definition: The value type is defined by the following
notation:
date-time = date "T" time ;As specified in the date and time
;value definitions
Description: If the property permits, multiple "date-time" values are
specified as a COMMA character (US-ASCII decimal 44) separated list
of values. No additional content value encoding (i.e., BACKSLASH
character encoding) is defined for this value type.
The "DATE-TIME" data type is used to identify values that contain a
precise calendar date and time of day. The format is based on the
[ISO 8601] complete representation, basic format for a calendar date
and time of day. The text format is a concatenation of the "date",
followed by the LATIN CAPITAL LETTER T character (US-ASCII decimal
84) time designator, followed by the "time" format.
The "DATE-TIME" data type expresses time values in three forms:
The form of date and time with UTC offset MUST NOT be used. For
example, the following is not valid for a date-time value:
Dawson & Stenerson Standards Track [Page 35]RFC 2445 iCalendar November 1998
DTSTART:19980119T230000-0800 ;Invalid time format
FORM #1: DATE WITH LOCAL TIME
The date with local time form is simply a date-time value that does
not contain the UTC designator nor does it reference a time zone. For
example, the following represents Janurary 18, 1998, at 11 PM:
DTSTART:19980118T230000
Date-time values of this type are said to be "floating" and are not
bound to any time zone in particular. They are used to represent the
same hour, minute, and second value regardless of which time zone is
currently being observed. For example, an event can be defined that
indicates that an individual will be busy from 11:00 AM to 1:00 PM
every day, no matter which time zone the person is in. In these
cases, a local time can be specified. The recipient of an iCalendar
object with a property value consisting of a local time, without any
relative time zone information, SHOULD interpret the value as being
fixed to whatever time zone the ATTENDEE is in at any given moment.
This means that two ATTENDEEs, in different time zones, receiving the
same event definition as a floating time, may be participating in the
event at different actual times. Floating time SHOULD only be used
where that is the reasonable behavior.
In most cases, a fixed time is desired. To properly communicate a
fixed time in a property value, either UTC time or local time with
time zone reference MUST be specified.
The use of local time in a DATE-TIME value without the TZID property
parameter is to be interpreted as floating time, regardless of the
existence of "VTIMEZONE" calendar components in the iCalendar object.
FORM #2: DATE WITH UTC TIME
The date with UTC time, or absolute time, is identified by a LATIN
CAPITAL LETTER Z suffix character (US-ASCII decimal 90), the UTC
designator, appended to the time value. For example, the following
represents January 19, 1998, at 0700 UTC:
DTSTART:19980119T070000Z
The TZID property parameter MUST NOT be applied to DATE-TIME
properties whose time values are specified in UTC.
FORM #3: DATE WITH LOCAL TIME AND TIME ZONE REFERENCE
Dawson & Stenerson Standards Track [Page 36]RFC 2445 iCalendar November 1998
The date and local time with reference to time zone information is
identified by the use the TZID property parameter to reference the
appropriate time zone definition. TZID is discussed in detail in the
section on Time Zone. For example, the following represents 2 AM in
New York on Janurary 19, 1998:
DTSTART;TZID=US-Eastern:19980119T020000
Example: The following represents July 14, 1997, at 1:30 PM in New
York City in each of the three time formats, using the "DTSTART"
property.
DTSTART:19970714T133000 ;Local time
DTSTART:19970714T173000Z ;UTC time
DTSTART;TZID=US-Eastern:19970714T133000 ;Local time and time
; zone reference
A time value MUST ONLY specify 60 seconds when specifying the
periodic "leap second" in the time value. For example:
COMPLETED:19970630T235960Z
4.3.6 Duration
Value Name: DURATION
Purpose: This value type is used to identify properties that contain
a duration of time.
Formal Definition: The value type is defined by the following
notation:
dur-value = (["+"] / "-") "P" (dur-date / dur-time / dur-week)
dur-date = dur-day [dur-time]
dur-time = "T" (dur-hour / dur-minute / dur-second)
dur-week = 1*DIGIT "W"
dur-hour = 1*DIGIT "H" [dur-minute]
dur-minute = 1*DIGIT "M" [dur-second]
dur-second = 1*DIGIT "S"
dur-day = 1*DIGIT "D"
Description: If the property permits, multiple "duration" values are
specified by a COMMA character (US-ASCII decimal 44) separated list
of values. The format is expressed as the [ISO 8601] basic format for
the duration of time. The format can represent durations in terms of
weeks, days, hours, minutes, and seconds.
Dawson & Stenerson Standards Track [Page 37]RFC 2445 iCalendar November 1998
No additional content value encoding (i.e., BACKSLASH character
encoding) are defined for this value type.
Example: A duration of 15 days, 5 hours and 20 seconds would be:
P15DT5H0M20S
A duration of 7 weeks would be:
P7W
4.3.7 Float
Value Name: FLOAT
Purpose: This value type is used to identify properties that contain
a real number value.
Formal Definition: The value type is defined by the following
notation:
float = (["+"] / "-") 1*DIGIT ["." 1*DIGIT]
Description: If the property permits, multiple "float" values are
specified by a COMMA character (US-ASCII decimal 44) separated list
of values.
No additional content value encoding (i.e., BACKSLASH character
encoding) is defined for this value type.
Example:
1000000.0000001
1.333
-3.14
4.3.8 Integer
Value Name:INTEGER
Purpose: This value type is used to identify properties that contain
a signed integer value.
Formal Definition: The value type is defined by the following
notation:
integer = (["+"] / "-") 1*DIGIT
Dawson & Stenerson Standards Track [Page 38]RFC 2445 iCalendar November 1998
Description: If the property permits, multiple "integer" values are
specified by a COMMA character (US-ASCII decimal 44) separated list
of values. The valid range for "integer" is -2147483648 to
2147483647. If the sign is not specified, then the value is assumed
to be positive.
No additional content value encoding (i.e., BACKSLASH character
encoding) is defined for this value type.
Example:
1234567890
-1234567890
+1234567890
432109876
4.3.9 Period of Time
Value Name: PERIOD
Purpose: This value type is used to identify values that contain a
precise period of time.
Formal Definition: The data type is defined by the following
notation:
period = period-explicit / period-start
period-explicit = date-time "/" date-time
; [ISO 8601] complete representation basic format for a period of
; time consisting of a start and end. The start MUST be before the
; end.
period-start = date-time "/" dur-value
; [ISO 8601] complete representation basic format for a period of
; time consisting of a start and positive duration of time.
Description: If the property permits, multiple "period" values are
specified by a COMMA character (US-ASCII decimal 44) separated list
of values. There are two forms of a period of time. First, a period
of time is identified by its start and its end. This format is
expressed as the [ISO 8601] complete representation, basic format for
"DATE-TIME" start of the period, followed by a SOLIDUS character
(US-ASCII decimal 47), followed by the "DATE-TIME" of the end of the
period. The start of the period MUST be before the end of the period.
Second, a period of time can also be defined by a start and a
positive duration of time. The format is expressed as the [ISO 8601]
complete representation, basic format for the "DATE-TIME" start of
Dawson & Stenerson Standards Track [Page 39]RFC 2445 iCalendar November 1998
the period, followed by a SOLIDUS character (US-ASCII decimal 47),
followed by the [ISO 8601] basic format for "DURATION" of the period.
Example: The period starting at 18:00:00 UTC, on January 1, 1997 and
ending at 07:00:00 UTC on January 2, 1997 would be:
19970101T180000Z/19970102T070000Z
The period start at 18:00:00 on January 1, 1997 and lasting 5 hours
and 30 minutes would be:
19970101T180000Z/PT5H30M
No additional content value encoding (i.e., BACKSLASH character
encoding) is defined for this value type.
4.3.10 Recurrence Rule
Value Name: RECUR
Purpose: This value type is used to identify properties that contain
a recurrence rule specification.
Formal Definition: The value type is defined by the following
notation:
recur = "FREQ"=freq *(
; either UNTIL or COUNT may appear in a 'recur',
; but UNTIL and COUNT MUST NOT occur in the same 'recur'
( ";" "UNTIL" "=" enddate ) /
( ";" "COUNT" "=" 1*DIGIT ) /
; the rest of these keywords are optional,
; but MUST NOT occur more than once
( ";" "INTERVAL" "=" 1*DIGIT ) /
( ";" "BYSECOND" "=" byseclist ) /
( ";" "BYMINUTE" "=" byminlist ) /
( ";" "BYHOUR" "=" byhrlist ) /
( ";" "BYDAY" "=" bywdaylist ) /
( ";" "BYMONTHDAY" "=" bymodaylist ) /
( ";" "BYYEARDAY" "=" byyrdaylist ) /
( ";" "BYWEEKNO" "=" bywknolist ) /
( ";" "BYMONTH" "=" bymolist ) /
( ";" "BYSETPOS" "=" bysplist ) /
( ";" "WKST" "=" weekday ) /
Dawson & Stenerson Standards Track [Page 40]RFC 2445 iCalendar November 1998
( ";" x-name "=" text )
)
freq = "SECONDLY" / "MINUTELY" / "HOURLY" / "DAILY"
/ "WEEKLY" / "MONTHLY" / "YEARLY"
enddate = date
enddate =/ date-time ;An UTC value
byseclist = seconds / ( seconds *("," seconds) )
seconds = 1DIGIT / 2DIGIT ;0 to 59
byminlist = minutes / ( minutes *("," minutes) )
minutes = 1DIGIT / 2DIGIT ;0 to 59
byhrlist = hour / ( hour *("," hour) )
hour = 1DIGIT / 2DIGIT ;0 to 23
bywdaylist = weekdaynum / ( weekdaynum *("," weekdaynum) )
weekdaynum = [([plus] ordwk / minus ordwk)] weekday
plus = "+"
minus = "-"
ordwk = 1DIGIT / 2DIGIT ;1 to 53
weekday = "SU" / "MO" / "TU" / "WE" / "TH" / "FR" / "SA"
;Corresponding to SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY,
;FRIDAY, SATURDAY and SUNDAY days of the week.
bymodaylist = monthdaynum / ( monthdaynum *("," monthdaynum) )
monthdaynum = ([plus] ordmoday) / (minus ordmoday)
ordmoday = 1DIGIT / 2DIGIT ;1 to 31
byyrdaylist = yeardaynum / ( yeardaynum *("," yeardaynum) )
yeardaynum = ([plus] ordyrday) / (minus ordyrday)
ordyrday = 1DIGIT / 2DIGIT / 3DIGIT ;1 to 366
bywknolist = weeknum / ( weeknum *("," weeknum) )
Dawson & Stenerson Standards Track [Page 41]RFC 2445 iCalendar November 1998
weeknum = ([plus] ordwk) / (minus ordwk)
bymolist = monthnum / ( monthnum *("," monthnum) )
monthnum = 1DIGIT / 2DIGIT ;1 to 12
bysplist = setposday / ( setposday *("," setposday) )
setposday = yeardaynum
Description: If the property permits, multiple "recur" values are
specified by a COMMA character (US-ASCII decimal 44) separated list
of values. The value type is a structured value consisting of a list
of one or more recurrence grammar parts. Each rule part is defined by
a NAME=VALUE pair. The rule parts are separated from each other by
the SEMICOLON character (US-ASCII decimal 59). The rule parts are not
ordered in any particular sequence. Individual rule parts MUST only
be specified once.
The FREQ rule part identifies the type of recurrence rule. This rule
part MUST be specified in the recurrence rule. Valid values include
SECONDLY, to specify repeating events based on an interval of a
second or more; MINUTELY, to specify repeating events based on an
interval of a minute or more; HOURLY, to specify repeating events
based on an interval of an hour or more; DAILY, to specify repeating
events based on an interval of a day or more; WEEKLY, to specify
repeating events based on an interval of a week or more; MONTHLY, to
specify repeating events based on an interval of a month or more; and
YEARLY, to specify repeating events based on an interval of a year or
more.
The INTERVAL rule part contains a positive integer representing how
often the recurrence rule repeats. The default value is "1", meaning
every second for a SECONDLY rule, or every minute for a MINUTELY
rule, every hour for an HOURLY rule, every day for a DAILY rule,
every week for a WEEKLY rule, every month for a MONTHLY rule and
every year for a YEARLY rule.
The UNTIL rule part defines a date-time value which bounds the
recurrence rule in an inclusive manner. If the value specified by
UNTIL is synchronized with the specified recurrence, this date or
date-time becomes the last instance of the recurrence. If specified
as a date-time value, then it MUST be specified in an UTC time
format. If not present, and the COUNT rule part is also not present,
the RRULE is considered to repeat forever.
The COUNT rule part defines the number of occurrences at which to
range-bound the recurrence. The "DTSTART" property value, if
Dawson & Stenerson Standards Track [Page 42]RFC 2445 iCalendar November 1998
specified, counts as the first occurrence.
The BYSECOND rule part specifies a COMMA character (US-ASCII decimal
44) separated list of seconds within a minute. Valid values are 0 to
59. The BYMINUTE rule part specifies a COMMA character (US-ASCII
decimal 44) separated list of minutes within an hour. Valid values
are 0 to 59. The BYHOUR rule part specifies a COMMA character (US-
ASCII decimal 44) separated list of hours of the day. Valid values
are 0 to 23.
The BYDAY rule part specifies a COMMA character (US-ASCII decimal 44)
separated list of days of the week; MO indicates Monday; TU indicates
Tuesday; WE indicates Wednesday; TH indicates Thursday; FR indicates
Friday; SA indicates Saturday; SU indicates Sunday.
Each BYDAY value can also be preceded by a positive (+n) or negative
(-n) integer. If present, this indicates the nth occurrence of the
specific day within the MONTHLY or YEARLY RRULE. For example, within
a MONTHLY rule, +1MO (or simply 1MO) represents the first Monday
within the month, whereas -1MO represents the last Monday of the
month. If an integer modifier is not present, it means all days of
this type within the specified frequency. For example, within a
MONTHLY rule, MO represents all Mondays within the month.
The BYMONTHDAY rule part specifies a COMMA character (ASCII decimal
44) separated list of days of the month. Valid values are 1 to 31 or
-31 to -1. For example, -10 represents the tenth to the last day of
the month.
The BYYEARDAY rule part specifies a COMMA character (US-ASCII decimal
44) separated list of days of the year. Valid values are 1 to 366 or
-366 to -1. For example, -1 represents the last day of the year
(December 31st) and -306 represents the 306th to the last day of the
year (March 1st).
The BYWEEKNO rule part specifies a COMMA character (US-ASCII decimal
44) separated list of ordinals specifying weeks of the year. Valid
values are 1 to 53 or -53 to -1. This corresponds to weeks according
to week numbering as defined in [ISO 8601]. A week is defined as a
seven day period, starting on the day of the week defined to be the
week start (see WKST). Week number one of the calendar year is the
first week which contains at least four (4) days in that calendar
year. This rule part is only valid for YEARLY rules. For example, 3
represents the third week of the year.
Note: Assuming a Monday week start, week 53 can only occur when
Thursday is January 1 or if it is a leap year and Wednesday is
January 1.
Dawson & Stenerson Standards Track [Page 43]RFC 2445 iCalendar November 1998
The BYMONTH rule part specifies a COMMA character (US-ASCII decimal
44) separated list of months of the year. Valid values are 1 to 12.
The WKST rule part specifies the day on which the workweek starts.
Valid values are MO, TU, WE, TH, FR, SA and SU. This is significant
when a WEEKLY RRULE has an interval greater than 1, and a BYDAY rule
part is specified. This is also significant when in a YEARLY RRULE
when a BYWEEKNO rule part is specified. The default value is MO.
The BYSETPOS rule part specifies a COMMA character (US-ASCII decimal
44) separated list of values which corresponds to the nth occurrence
within the set of events specified by the rule. Valid values are 1 to
366 or -366 to -1. It MUST only be used in conjunction with another
BYxxx rule part. For example "the last work day of the month" could
be represented as:
RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-1
Each BYSETPOS value can include a positive (+n) or negative (-n)
integer. If present, this indicates the nth occurrence of the
specific occurrence within the set of events specified by the rule.
If BYxxx rule part values are found which are beyond the available
scope (ie, BYMONTHDAY=30 in February), they are simply ignored.
Information, not contained in the rule, necessary to determine the
various recurrence instance start time and dates are derived from the
Start Time (DTSTART) entry attribute. For example,
"FREQ=YEARLY;BYMONTH=1" doesn't specify a specific day within the
month or a time. This information would be the same as what is
specified for DTSTART.
BYxxx rule parts modify the recurrence in some manner. BYxxx rule
parts for a period of time which is the same or greater than the
frequency generally reduce or limit the number of occurrences of the
recurrence generated. For example, "FREQ=DAILY;BYMONTH=1" reduces the
number of recurrence instances from all days (if BYMONTH tag is not
present) to all days in January. BYxxx rule parts for a period of
time less than the frequency generally increase or expand the number
of occurrences of the recurrence. For example,
"FREQ=YEARLY;BYMONTH=1,2" increases the number of days within the
yearly recurrence set from 1 (if BYMONTH tag is not present) to 2.
If multiple BYxxx rule parts are specified, then after evaluating the
specified FREQ and INTERVAL rule parts, the BYxxx rule parts are
applied to the current set of evaluated occurrences in the following
order: BYMONTH, BYWEEKNO, BYYEARDAY, BYMONTHDAY, BYDAY, BYHOUR,
BYMINUTE, BYSECOND and BYSETPOS; then COUNT and UNTIL are evaluated.
Dawson & Stenerson Standards Track [Page 44]RFC 2445 iCalendar November 1998
Here is an example of evaluating multiple BYxxx rule parts.
DTSTART;TZID=US-Eastern:19970105T083000
RRULE:FREQ=YEARLY;INTERVAL=2;BYMONTH=1;BYDAY=SU;BYHOUR=8,9;
BYMINUTE=30
First, the "INTERVAL=2" would be applied to "FREQ=YEARLY" to arrive
at "every other year". Then, "BYMONTH=1" would be applied to arrive
at "every January, every other year". Then, "BYDAY=SU" would be
applied to arrive at "every Sunday in January, every other year".
Then, "BYHOUR=8,9" would be applied to arrive at "every Sunday in
January at 8 AM and 9 AM, every other year". Then, "BYMINUTE=30"
would be applied to arrive at "every Sunday in January at 8:30 AM and
9:30 AM, every other year". Then, lacking information from RRULE, the
second is derived from DTSTART, to end up in "every Sunday in January
at 8:30:00 AM and 9:30:00 AM, every other year". Similarly, if the
BYMINUTE, BYHOUR, BYDAY, BYMONTHDAY or BYMONTH rule part were
missing, the appropriate minute, hour, day or month would have been
retrieved from the "DTSTART" property.
No additional content value encoding (i.e., BACKSLASH character
encoding) is defined for this value type.
Example: The following is a rule which specifies 10 meetings which
occur every other day:
FREQ=DAILY;COUNT=10;INTERVAL=2
There are other examples specified in the "RRULE" specification.
4.3.11 Text
Value Name: TEXT
Purpose This value type is used to identify values that contain human
readable text.
Formal Definition: The character sets supported by this revision of
iCalendar are UTF-8 and US ASCII thereof. The applicability to other
character sets is for future work. The value type is defined by the
following notation.
text = *(TSAFE-CHAR / ":" / DQUOTE / ESCAPED-CHAR)
; Folded according to description above
ESCAPED-CHAR = "\\" / "\;" / "\," / "\N" / "\n")
; \\ encodes \, \N or \n encodes newline
; \; encodes ;, \, encodes ,
Dawson & Stenerson Standards Track [Page 45]RFC 2445 iCalendar November 1998
TSAFE-CHAR = %x20-21 / %x23-2B / %x2D-39 / %x3C-5B
%x5D-7E / NON-US-ASCII
; Any character except CTLs not needed by the current
; character set, DQUOTE, ";", ":", "\", ","
Note: Certain other character sets may require modification of the
above definitions, but this is beyond the scope of this document.
Description: If the property permits, multiple "text" values are
specified by a COMMA character (US-ASCII decimal 44) separated list
of values.
The language in which the text is represented can be controlled by
the "LANGUAGE" property parameter.
An intentional formatted text line break MUST only be included in a
"TEXT" property value by representing the line break with the
character sequence of BACKSLASH (US-ASCII decimal 92), followed by a
LATIN SMALL LETTER N (US-ASCII decimal 110) or a LATIN CAPITAL LETTER
N (US-ASCII decimal 78), that is "\n" or "\N".
The "TEXT" property values may also contain special characters that
are used to signify delimiters, such as a COMMA character for lists
of values or a SEMICOLON character for structured values. In order to
support the inclusion of these special characters in "TEXT" property
values, they MUST be escaped with a BACKSLASH character. A BACKSLASH
character (US-ASCII decimal 92) in a "TEXT" property value MUST be
escaped with another BACKSLASH character. A COMMA character in a
"TEXT" property value MUST be escaped with a BACKSLASH character
(US-ASCII decimal 92). A SEMICOLON character in a "TEXT" property
value MUST be escaped with a BACKSLASH character (US-ASCII decimal
92). However, a COLON character in a "TEXT" property value SHALL NOT
be escaped with a BACKSLASH character.Example: A multiple line value
of:
Project XYZ Final Review
Conference Room - 3B
Come Prepared.
would be represented as:
Project XYZ Final Review\nConference Room - 3B\nCome Prepared.
Dawson & Stenerson Standards Track [Page 46]RFC 2445 iCalendar November 1998
4.3.12 Time
Value Name: TIME
Purpose: This value type is used to identify values that contain a
time of day.
Formal Definition: The data type is defined by the following
notation:
time = time-hour time-minute time-second [time-utc]
time-hour = 2DIGIT ;00-23
time-minute = 2DIGIT ;00-59
time-second = 2DIGIT ;00-60
;The "60" value is used to account for "leap" seconds.
time-utc = "Z"
Description: If the property permits, multiple "time" values are
specified by a COMMA character (US-ASCII decimal 44) separated list
of values. No additional content value encoding (i.e., BACKSLASH
character encoding) is defined for this value type.
The "TIME" data type is used to identify values that contain a time
of day. The format is based on the [ISO 8601] complete
representation, basic format for a time of day. The text format
consists of a two-digit 24-hour of the day (i.e., values 0-23), two-
digit minute in the hour (i.e., values 0-59), and two-digit seconds
in the minute (i.e., values 0-60). The seconds value of 60 MUST only
to be used to account for "leap" seconds. Fractions of a second are
not supported by this format.
In parallel to the "DATE-TIME" definition above, the "TIME" data type
expresses time values in three forms:
The form of time with UTC offset MUST NOT be used. For example, the
following is NOT VALID for a time value:
230000-0800 ;Invalid time format
FORM #1 LOCAL TIME
The local time form is simply a time value that does not contain the
UTC designator nor does it reference a time zone. For example, 11:00
PM:
230000
Dawson & Stenerson Standards Track [Page 47]RFC 2445 iCalendar November 1998
Time values of this type are said to be "floating" and are not bound
to any time zone in particular. They are used to represent the same
hour, minute, and second value regardless of which time zone is
currently being observed. For example, an event can be defined that
indicates that an individual will be busy from 11:00 AM to 1:00 PM
every day, no matter which time zone the person is in. In these
cases, a local time can be specified. The recipient of an iCalendar
object with a property value consisting of a local time, without any
relative time zone information, SHOULD interpret the value as being
fixed to whatever time zone the ATTENDEE is in at any given moment.
This means that two ATTENDEEs may participate in the same event at
different UTC times; floating time SHOULD only be used where that is
reasonable behavior.
In most cases, a fixed time is desired. To properly communicate a
fixed time in a property value, either UTC time or local time with
time zone reference MUST be specified.
The use of local time in a TIME value without the TZID property
parameter is to be interpreted as a local time value, regardless of
the existence of "VTIMEZONE" calendar components in the iCalendar
object.
FORM #2: UTC TIME
UTC time, or absolute time, is identified by a LATIN CAPITAL LETTER Z
suffix character (US-ASCII decimal 90), the UTC designator, appended
to the time value. For example, the following represents 07:00 AM
UTC:
070000Z
The TZID property parameter MUST NOT be applied to TIME properties
whose time values are specified in UTC.
FORM #3: LOCAL TIME AND TIME ZONE REFERENCE
The local time with reference to time zone information form is
identified by the use the TZID property parameter to reference the
appropriate time zone definition. TZID is discussed in detail in the
section on Time Zone.
Example: The following represents 8:30 AM in New York in Winter, five
hours behind UTC, in each of the three formats using the "X-
TIMEOFDAY" non-standard property:
Dawson & Stenerson Standards Track [Page 48]RFC 2445 iCalendar November 1998
X-TIMEOFDAY:083000
X-TIMEOFDAY:133000Z
X-TIMEOFDAY;TZID=US-Eastern:083000
4.3.13 URI
Value Name: URI
Purpose: This value type is used to identify values that contain a
uniform resource identifier (URI) type of reference to the property
value.
Formal Definition: The data type is defined by the following
notation:
uri = <As defined by any IETF RFC>
Description: This data type might be used to reference binary
information, for values that are large, or otherwise undesirable to
include directly in the iCalendar object.
The URI value formats in RFC 1738, RFC 2111 and any other IETF
registered value format can be specified.
Any IANA registered URI format can be used. These include, but are
not limited to, those defined in RFC 1738 and RFC 2111.
When a property parameter value is a URI value type, the URI MUST be
specified as a quoted-string value.
No additional content value encoding (i.e., BACKSLASH character
encoding) is defined for this value type.
Example: The following is a URI for a network file:
http://host1.com/my-report.txt
4.3.14 UTC Offset
Value Name: UTC-OFFSET
Purpose: This value type is used to identify properties that contain
an offset from UTC to local time.
Formal Definition: The data type is defined by the following
notation:
Dawson & Stenerson Standards Track [Page 49]RFC 2445 iCalendar November 1998
utc-offset = time-numzone ;As defined above in time data type
time-numzone = ("+" / "-") time-hour time-minute [time-
second]
Description: The PLUS SIGN character MUST be specified for positive
UTC offsets (i.e., ahead of UTC). The value of "-0000" and "-000000"
are not allowed. The time-second, if present, may not be 60; if
absent, it defaults to zero.
No additional content value encoding (i.e., BACKSLASH character
encoding) is defined for this value type.
Example: The following UTC offsets are given for standard time for
New York (five hours behind UTC) and Geneva (one hour ahead of UTC):
-0500
+0100
4.4 iCalendar Object
The Calendaring and Scheduling Core Object is a collection of
calendaring and scheduling information. Typically, this information
will consist of a single iCalendar object. However, multiple
iCalendar objects can be sequentially grouped together. The first
line and last line of the iCalendar object MUST contain a pair of
iCalendar object delimiter strings. The syntax for an iCalendar
object is as follows:
icalobject = 1*("BEGIN" ":" "VCALENDAR" CRLF
icalbody
"END" ":" "VCALENDAR" CRLF)
The following is a simple example of an iCalendar object:
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//hacksw/handcal//NONSGML v1.0//EN
BEGIN:VEVENT
DTSTART:19970714T170000Z
DTEND:19970715T035959Z
SUMMARY:Bastille Day Party
END:VEVENT
END:VCALENDAR
Dawson & Stenerson Standards Track [Page 50]RFC 2445 iCalendar November 1998
4.5 Property
A property is the definition of an individual attribute describing a
calendar or a calendar component. A property takes the form defined
by the "contentline" notation defined in section 4.1.1.
The following is an example of a property:
DTSTART:19960415T133000Z
This memo imposes no ordering of properties within an iCalendar
object.
Property names, parameter names and enumerated parameter values are
case insensitive. For example, the property name "DUE" is the same as
"due" and "Due", DTSTART;TZID=US-Eastern:19980714T120000 is the same
as DtStart;TzID=US-Eastern:19980714T120000.
4.6 Calendar Components
The body of the iCalendar object consists of a sequence of calendar
properties and one or more calendar components. The calendar
properties are attributes that apply to the calendar as a whole. The
calendar components are collections of properties that express a
particular calendar semantic. For example, the calendar component can
specify an event, a to-do, a journal entry, time zone information, or
free/busy time information, or an alarm.
The body of the iCalendar object is defined by the following
notation:
icalbody = calprops component
calprops = 2*(
; 'prodid' and 'version' are both REQUIRED,
; but MUST NOT occur more than once
prodid /version /
; 'calscale' and 'method' are optional,
; but MUST NOT occur more than once
calscale /
method /
x-prop
Dawson & Stenerson Standards Track [Page 51]RFC 2445 iCalendar November 1998
)
component = 1*(eventc / todoc / journalc / freebusyc /
/ timezonec / iana-comp / x-comp)
iana-comp = "BEGIN" ":" iana-token CRLF
1*contentline
"END" ":" iana-token CRLF
x-comp = "BEGIN" ":" x-name CRLF
1*contentline
"END" ":" x-name CRLF
An iCalendar object MUST include the "PRODID" and "VERSION" calendar
properties. In addition, it MUST include at least one calendar
component. Special forms of iCalendar objects are possible to publish
just busy time (i.e., only a "VFREEBUSY" calendar component) or time
zone (i.e., only a "VTIMEZONE" calendar component) information. In
addition, a complex iCalendar object is possible that is used to
capture a complete snapshot of the contents of a calendar (e.g.,
composite of many different calendar components). More commonly, an
iCalendar object will consist of just a single "VEVENT", "VTODO" or
"VJOURNAL" calendar component.
4.6.1 Event Component
Component Name: "VEVENT"
Purpose: Provide a grouping of component properties that describe an
event.
Format Definition: A "VEVENT" calendar component is defined by the
following notation:
eventc = "BEGIN" ":" "VEVENT" CRLF
eventprop *alarmc
"END" ":" "VEVENT" CRLF
eventprop = *(
; the following are optional,
; but MUST NOT occur more than once
class / created / description / dtstart / geo /
Dawson & Stenerson Standards Track [Page 52]RFC 2445 iCalendar November 1998
last-mod / location / organizer / priority /
dtstamp / seq / status / summary / transp /
uid / url / recurid /
; either 'dtend' or 'duration' may appear in
; a 'eventprop', but 'dtend' and 'duration'
; MUST NOT occur in the same 'eventprop'
dtend / duration /
; the following are optional,
; and MAY occur more than once
attach / attendee / categories / comment /
contact / exdate / exrule / rstatus / related /
resources / rdate / rrule / x-prop
)
Description: A "VEVENT" calendar component is a grouping of component
properties, and possibly including "VALARM" calendar components, that
represents a scheduled amount of time on a calendar. For example, it
can be an activity; such as a one-hour long, department meeting from
8:00 AM to 9:00 AM, tomorrow. Generally, an event will take up time
on an individual calendar. Hence, the event will appear as an opaque
interval in a search for busy time. Alternately, the event can have
its Time Transparency set to "TRANSPARENT" in order to prevent
blocking of the event in searches for busy time.
The "VEVENT" is also the calendar component used to specify an
anniversary or daily reminder within a calendar. These events have a
DATE value type for the "DTSTART" property instead of the default
data type of DATE-TIME. If such a "VEVENT" has a "DTEND" property, it
MUST be specified as a DATE value also. The anniversary type of
"VEVENT" can span more than one date (i.e, "DTEND" property value is
set to a calendar date after the "DTSTART" property value).
The "DTSTART" property for a "VEVENT" specifies the inclusive start
of the event. For recurring events, it also specifies the very first
instance in the recurrence set. The "DTEND" property for a "VEVENT"
calendar component specifies the non-inclusive end of the event. For
cases where a "VEVENT" calendar component specifies a "DTSTART"
property with a DATE data type but no "DTEND" property, the events
non-inclusive end is the end of the calendar date specified by the
"DTSTART" property. For cases where a "VEVENT" calendar component
specifies a "DTSTART" property with a DATE-TIME data type but no
"DTEND" property, the event ends on the same calendar date and time
of day specified by the "DTSTART" property.
Dawson & Stenerson Standards Track [Page 53]RFC 2445 iCalendar November 1998
The "VEVENT" calendar component cannot be nested within another
calendar component. However, "VEVENT" calendar components can be
related to each other or to a "VTODO" or to a "VJOURNAL" calendar
component with the "RELATED-TO" property.
Example: The following is an example of the "VEVENT" calendar
component used to represent a meeting that will also be opaque to
searches for busy time:
BEGIN:VEVENT
UID:19970901T130000Z-123401@host.com
DTSTAMP:19970901T1300Z
DTSTART:19970903T163000Z
DTEND:19970903T190000Z
SUMMARY:Annual Employee Review
CLASS:PRIVATE
CATEGORIES:BUSINESS,HUMAN RESOURCES
END:VEVENT
The following is an example of the "VEVENT" calendar component used
to represent a reminder that will not be opaque, but rather
transparent, to searches for busy time:
BEGIN:VEVENT
UID:19970901T130000Z-123402@host.com
DTSTAMP:19970901T1300Z
DTSTART:19970401T163000Z
DTEND:19970402T010000Z
SUMMARY:Laurel is in sensitivity awareness class.
CLASS:PUBLIC
CATEGORIES:BUSINESS,HUMAN RESOURCES
TRANSP:TRANSPARENT
END:VEVENT
The following is an example of the "VEVENT" calendar component used
to represent an anniversary that will occur annually. Since it takes
up no time, it will not appear as opaque in a search for busy time;
no matter what the value of the "TRANSP" property indicates:
BEGIN:VEVENT
UID:19970901T130000Z-123403@host.com
DTSTAMP:19970901T1300Z
DTSTART:19971102
SUMMARY:Our Blissful Anniversary
CLASS:CONFIDENTIAL
CATEGORIES:ANNIVERSARY,PERSONAL,SPECIAL OCCASION
RRULE:FREQ=YEARLY
END:VEVENT
Dawson & Stenerson Standards Track [Page 54]RFC 2445 iCalendar November 1998
4.6.2 To-do Component
Component Name: VTODO
Purpose: Provide a grouping of calendar properties that describe a
to-do.
Formal Definition: A "VTODO" calendar component is defined by the
following notation:
todoc = "BEGIN" ":" "VTODO" CRLF
todoprop *alarmc
"END" ":" "VTODO" CRLF
todoprop = *(
; the following are optional,
; but MUST NOT occur more than once
class / completed / created / description / dtstamp /
dtstart / geo / last-mod / location / organizer /
percent / priority / recurid / seq / status /
summary / uid / url /
; either 'due' or 'duration' may appear in
; a 'todoprop', but 'due' and 'duration'
; MUST NOT occur in the same 'todoprop'
due / duration /
; the following are optional,
; and MAY occur more than once
attach / attendee / categories / comment / contact /
exdate / exrule / rstatus / related / resources /
rdate / rrule / x-prop
)
Description: A "VTODO" calendar component is a grouping of component
properties and possibly "VALARM" calendar components that represent
an action-item or assignment. For example, it can be used to
represent an item of work assigned to an individual; such as "turn in
travel expense today".
The "VTODO" calendar component cannot be nested within another
calendar component. However, "VTODO" calendar components can be
related to each other or to a "VTODO" or to a "VJOURNAL" calendar
component with the "RELATED-TO" property.
Dawson & Stenerson Standards Track [Page 55]RFC 2445 iCalendar November 1998
A "VTODO" calendar component without the "DTSTART" and "DUE" (or
"DURATION") properties specifies a to-do that will be associated with
each successive calendar date, until it is completed.
Example: The following is an example of a "VTODO" calendar component:
BEGIN:VTODO
UID:19970901T130000Z-123404@host.com
DTSTAMP:19970901T1300Z
DTSTART:19970415T133000Z
DUE:19970416T045959Z
SUMMARY:1996 Income Tax Preparation
CLASS:CONFIDENTIAL
CATEGORIES:FAMILY,FINANCE
PRIORITY:1
STATUS:NEEDS-ACTION
END:VTODO
4.6.3 Journal Component
Component Name: VJOURNAL
Purpose: Provide a grouping of component properties that describe a
journal entry.
Formal Definition: A "VJOURNAL" calendar component is defined by the
following notation:
journalc = "BEGIN" ":" "VJOURNAL" CRLF
jourprop
"END" ":" "VJOURNAL" CRLF
jourprop = *(
; the following are optional,
; but MUST NOT occur more than once
class / created / description / dtstart / dtstamp /
last-mod / organizer / recurid / seq / status /
summary / uid / url /
; the following are optional,
; and MAY occur more than once
attach / attendee / categories / comment /
contact / exdate / exrule / related / rdate /
rrule / rstatus / x-prop
Dawson & Stenerson Standards Track [Page 56]RFC 2445 iCalendar November 1998
)
Description: A "VJOURNAL" calendar component is a grouping of
component properties that represent one or more descriptive text
notes associated with a particular calendar date. The "DTSTART"
property is used to specify the calendar date that the journal entry
is associated with. Generally, it will have a DATE value data type,
but it can also be used to specify a DATE-TIME value data type.
Examples of a journal entry include a daily record of a legislative
body or a journal entry of individual telephone contacts for the day
or an ordered list of accomplishments for the day. The "VJOURNAL"
calendar component can also be used to associate a document with a
calendar date.
The "VJOURNAL" calendar component does not take up time on a
calendar. Hence, it does not play a role in free or busy time
searches - - it is as though it has a time transparency value of
TRANSPARENT. It is transparent to any such searches.
The "VJOURNAL" calendar component cannot be nested within another
calendar component. However, "VJOURNAL" calendar components can be
related to each other or to a "VEVENT" or to a "VTODO" calendar
component, with the "RELATED-TO" property.
Example: The following is an example of the "VJOURNAL" calendar
component:
BEGIN:VJOURNAL
UID:19970901T130000Z-123405@host.com
DTSTAMP:19970901T1300Z
DTSTART;VALUE=DATE:19970317
SUMMARY:Staff meeting minutes
DESCRIPTION:1. Staff meeting: Participants include Joe\, Lisa
and Bob. Aurora project plans were reviewed. There is currently
no budget reserves for this project. Lisa will escalate to
management. Next meeting on Tuesday.\n
2. Telephone Conference: ABC Corp. sales representative called
to discuss new printer. Promised to get us a demo by Friday.\n
3. Henry Miller (Handsoff Insurance): Car was totaled by tree.
Is looking into a loaner car. 654-2323 (tel).
END:VJOURNAL
Dawson & Stenerson Standards Track [Page 57]RFC 2445 iCalendar November 1998
4.6.4 Free/Busy Component
Component Name: VFREEBUSY
Purpose: Provide a grouping of component properties that describe
either a request for free/busy time, describe a response to a request
for free/busy time or describe a published set of busy time.
Formal Definition: A "VFREEBUSY" calendar component is defined by the
following notation:
freebusyc = "BEGIN" ":" "VFREEBUSY" CRLF
fbprop
"END" ":" "VFREEBUSY" CRLF
fbprop = *(
; the following are optional,
; but MUST NOT occur more than once
contact / dtstart / dtend / duration / dtstamp /
organizer / uid / url /
; the following are optional,
; and MAY occur more than once
attendee / comment / freebusy / rstatus / x-prop
)
Description: A "VFREEBUSY" calendar component is a grouping of
component properties that represents either a request for, a reply to
a request for free or busy time information or a published set of
busy time information.
When used to request free/busy time information, the "ATTENDEE"
property specifies the calendar users whose free/busy time is being
requested; the "ORGANIZER" property specifies the calendar user who
is requesting the free/busy time; the "DTSTART" and "DTEND"
properties specify the window of time for which the free/busy time is
being requested; the "UID" and "DTSTAMP" properties are specified to
assist in proper sequencing of multiple free/busy time requests.
When used to reply to a request for free/busy time, the "ATTENDEE"
property specifies the calendar user responding to the free/busy time
request; the "ORGANIZER" property specifies the calendar user that
originally requested the free/busy time; the "FREEBUSY" property
specifies the free/busy time information (if it exists); and the
Dawson & Stenerson Standards Track [Page 58]RFC 2445 iCalendar November 1998
"UID" and "DTSTAMP" properties are specified to assist in proper
sequencing of multiple free/busy time replies.
When used to publish busy time, the "ORGANIZER" property specifies
the calendar user associated with the published busy time; the
"DTSTART" and "DTEND" properties specify an inclusive time window
that surrounds the busy time information; the "FREEBUSY" property
specifies the published busy time information; and the "DTSTAMP"
property specifies the date/time that iCalendar object was created.
The "VFREEBUSY" calendar component cannot be nested within another
calendar component. Multiple "VFREEBUSY" calendar components can be
specified within an iCalendar object. This permits the grouping of
Free/Busy information into logical collections, such as monthly
groups of busy time information.
The "VFREEBUSY" calendar component is intended for use in iCalendar
object methods involving requests for free time, requests for busy
time, requests for both free and busy, and the associated replies.
Free/Busy information is represented with the "FREEBUSY" property.
This property provides a terse representation of time periods. One or
more "FREEBUSY" properties can be specified in the "VFREEBUSY"
calendar component.
When present in a "VFREEBUSY" calendar component, the "DTSTART" and
"DTEND" properties SHOULD be specified prior to any "FREEBUSY"
properties. In a free time request, these properties can be used in
combination with the "DURATION" property to represent a request for a
duration of free time within a specified window of time.
The recurrence properties ("RRULE", "EXRULE", "RDATE", "EXDATE") are
not permitted within a "VFREEBUSY" calendar component. Any recurring
events are resolved into their individual busy time periods using the
"FREEBUSY" property.
Example: The following is an example of a "VFREEBUSY" calendar
component used to request free or busy time information:
BEGIN:VFREEBUSY
ORGANIZER:MAILTO:jane_doe@host1.com
ATTENDEE:MAILTO:john_public@host2.com
DTSTART:19971015T050000Z
DTEND:19971016T050000Z
DTSTAMP:19970901T083000Z
END:VFREEBUSY
Dawson & Stenerson Standards Track [Page 59]RFC 2445 iCalendar November 1998
The following is an example of a "VFREEBUSY" calendar component used
to reply to the request with busy time information:
BEGIN:VFREEBUSY
ORGANIZER:MAILTO:jane_doe@host1.com
ATTENDEE:MAILTO:john_public@host2.com
DTSTAMP:19970901T100000Z
FREEBUSY;VALUE=PERIOD:19971015T050000Z/PT8H30M,
19971015T160000Z/PT5H30M,19971015T223000Z/PT6H30M
URL:http://host2.com/pub/busy/jpublic-01.ifb
COMMENT:This iCalendar file contains busy time information for
the next three months.
END:VFREEBUSY
The following is an example of a "VFREEBUSY" calendar component used
to publish busy time information.
BEGIN:VFREEBUSY
ORGANIZER:jsmith@host.com
DTSTART:19980313T141711Z
DTEND:19980410T141711Z
FREEBUSY:19980314T233000Z/19980315T003000Z
FREEBUSY:19980316T153000Z/19980316T163000Z
FREEBUSY:19980318T030000Z/19980318T040000Z
URL:http://www.host.com/calendar/busytime/jsmith.ifb
END:VFREEBUSY
4.6.5 Time Zone Component
Component Name: VTIMEZONE
Purpose: Provide a grouping of component properties that defines a
time zone.
Formal Definition: A "VTIMEZONE" calendar component is defined by the
following notation:
timezonec = "BEGIN" ":" "VTIMEZONE" CRLF
2*(
; 'tzid' is required, but MUST NOT occur more
; than once
tzid /
; 'last-mod' and 'tzurl' are optional,
but MUST NOT occur more than once
Dawson & Stenerson Standards Track [Page 60]RFC 2445 iCalendar November 1998
last-mod / tzurl /
; one of 'standardc' or 'daylightc' MUST occur
..; and each MAY occur more than once.
standardc / daylightc /
; the following is optional,
; and MAY occur more than once
x-prop
)
"END" ":" "VTIMEZONE" CRLF
standardc = "BEGIN" ":" "STANDARD" CRLF
tzprop
"END" ":" "STANDARD" CRLF
daylightc = "BEGIN" ":" "DAYLIGHT" CRLF
tzprop
"END" ":" "DAYLIGHT" CRLF
tzprop = 3*(
; the following are each REQUIRED,
; but MUST NOT occur more than once
dtstart / tzoffsetto / tzoffsetfrom /
; the following are optional,
; and MAY occur more than once
comment / rdate / rrule / tzname / x-prop
)
Description: A time zone is unambiguously defined by the set of time
measurement rules determined by the governing body for a given
geographic area. These rules describe at a minimum the base offset
from UTC for the time zone, often referred to as the Standard Time
offset. Many locations adjust their Standard Time forward or backward
by one hour, in order to accommodate seasonal changes in number of
Dawson & Stenerson Standards Track [Page 61]RFC 2445 iCalendar November 1998
daylight hours, often referred to as Daylight Saving Time. Some
locations adjust their time by a fraction of an hour. Standard Time
is also known as Winter Time. Daylight Saving Time is also known as
Advanced Time, Summer Time, or Legal Time in certain countries. The
following table shows the changes in time zone rules in effect for
New York City starting from 1967. Each line represents a description
or rule for a particular observance.
Effective Observance Rule
Date (Date/Time) Offset Abbreviation
1967-* last Sun in Oct, 02:00 -0500 EST
1967-1973 last Sun in Apr, 02:00 -0400 EDT
1974-1974 Jan 6, 02:00 -0400 EDT
1975-1975 Feb 23, 02:00 -0400 EDT
1976-1986 last Sun in Apr, 02:00 -0400 EDT
1987-* first Sun in Apr, 02:00 -0400 EDT
Note: The specification of a global time zone registry is not
addressed by this document and is left for future study.
However, implementers may find the Olson time zone database [TZ]
a useful reference. It is an informal, public-domain collection
of time zone information, which is currently being maintained by
volunteer Internet participants, and is used in several
operating systems. This database contains current and historical
time zone information for a wide variety of locations around the
globe; it provides a time zone identifier for every unique time
zone rule set in actual use since 1970, with historical data
going back to the introduction of standard time.
Interoperability between two calendaring and scheduling applications,
especially for recurring events, to-dos or journal entries, is
dependent on the ability to capture and convey date and time
information in an unambiguous format. The specification of current
time zone information is integral to this behavior.
If present, the "VTIMEZONE" calendar component defines the set of
Standard Time and Daylight Saving Time observances (or rules) for a
particular time zone for a given interval of time. The "VTIMEZONE"
calendar component cannot be nested within other calendar components.
Multiple "VTIMEZONE" calendar components can exist in an iCalendar
object. In this situation, each "VTIMEZONE" MUST represent a unique
Dawson & Stenerson Standards Track [Page 62]RFC 2445 iCalendar November 1998
time zone definition. This is necessary for some classes of events,
such as airline flights, that start in one time zone and end in
another.
The "VTIMEZONE" calendar component MUST be present if the iCalendar
object contains an RRULE that generates dates on both sides of a time
zone shift (e.g. both in Standard Time and Daylight Saving Time)
unless the iCalendar object intends to convey a floating time (See
the section "4.1.10.11 Time" for proper interpretation of floating
time). It can be present if the iCalendar object does not contain
such a RRULE. In addition, if a RRULE is present, there MUST be valid
time zone information for all recurrence instances.
The "VTIMEZONE" calendar component MUST include the "TZID" property
and at least one definition of a standard or daylight component. The
standard or daylight component MUST include the "DTSTART",
"TZOFFSETFROM" and "TZOFFSETTO" properties.
An individual "VTIMEZONE" calendar component MUST be specified for
each unique "TZID" parameter value specified in the iCalendar object.
Each "VTIMEZONE" calendar component consists of a collection of one
or more sub-components that describe the rule for a particular
observance (either a Standard Time or a Daylight Saving Time
observance). The "STANDARD" sub-component consists of a collection of
properties that describe Standard Time. The "DAYLIGHT" sub-component
consists of a collection of properties that describe Daylight Saving
Time. In general this collection of properties consists of:
- the first onset date-time for the observance
- the last onset date-time for the observance, if a last onset
is known.
- the offset to be applied for the observance
- a rule that describes the day and time when the observance
takes effect
- an optional name for the observance
For a given time zone, there may be multiple unique definitions of
the observances over a period of time. Each observance is described
using either a "STANDARD" or "DAYLIGHT" sub-component. The collection
of these sub-components is used to describe the time zone for a given
period of time. The offset to apply at any given time is found by
locating the observance that has the last onset date and time before
the time in question, and using the offset value from that
Dawson & Stenerson Standards Track [Page 63]RFC 2445 iCalendar November 1998
observance.
The top-level properties in a "VTIMEZONE" calendar component are:
The mandatory "TZID" property is a text value that uniquely
identifies the VTIMZONE calendar component within the scope of an
iCalendar object.
The optional "LAST-MODIFIED" property is a UTC value that specifies
the date and time that this time zone definition was last updated.
The optional "TZURL" property is url value that points to a published
VTIMEZONE definition. TZURL SHOULD refer to a resource that is
accessible by anyone who might need to interpret the object. This
SHOULD NOT normally be a file: URL or other URL that is not widely-
accessible.
The collection of properties that are used to define the STANDARD and
DAYLIGHT sub-components include:
The mandatory "DTSTART" property gives the effective onset date and
local time for the time zone sub-component definition. "DTSTART" in
this usage MUST be specified as a local DATE-TIME value.
The mandatory "TZOFFSETFROM" property gives the UTC offset which is
in use when the onset of this time zone observance begins.
"TZOFFSETFROM" is combined with "DTSTART" to define the effective
onset for the time zone sub-component definition. For example, the
following represents the time at which the observance of Standard
Time took effect in Fall 1967 for New York City:
DTSTART:19671029T020000
TZOFFSETFROM:-0400
The mandatory "TZOFFSETTO " property gives the UTC offset for the
time zone sub-component (Standard Time or Daylight Saving Time) when
this observance is in use.
The optional "TZNAME" property is the customary name for the time
zone. It may be specified multiple times, to allow for specifying
multiple language variants of the time zone names. This could be used
for displaying dates.
If specified, the onset for the observance defined by the time zone
sub-component is defined by either the "RRULE" or "RDATE" property.
If neither is specified, only one sub-component can be specified in
the "VTIMEZONE" calendar component and it is assumed that the single
Dawson & Stenerson Standards Track [Page 64]RFC 2445 iCalendar November 1998
observance specified is always in effect.
The "RRULE" property defines the recurrence rule for the onset of the
observance defined by this time zone sub-component. Some specific
requirements for the usage of RRULE for this purpose include:
- If observance is known to have an effective end date, the
"UNTIL" recurrence rule parameter MUST be used to specify the
last valid onset of this observance (i.e., the UNTIL date-time
will be equal to the last instance generated by the recurrence
pattern). It MUST be specified in UTC time.
- The "DTSTART" and the "TZOFFSETTO" properties MUST be used
when generating the onset date-time values (instances) from the
RRULE.
Alternatively, the "RDATE" property can be used to define the onset
of the observance by giving the individual onset date and times.
"RDATE" in this usage MUST be specified as a local DATE-TIME value in
UTC time.
The optional "COMMENT" property is also allowed for descriptive
explanatory text.
Example: The following are examples of the "VTIMEZONE" calendar
component:
This is an example showing time zone information for the Eastern
United States using "RDATE" property. Note that this is only suitable
for a recurring event that starts on or later than April 6, 1997 at
03:00:00 EDT (i.e., the earliest effective transition date and time)
and ends no later than April 7, 1998 02:00:00 EST (i.e., latest valid
date and time for EST in this scenario). For example, this can be
used for a recurring event that occurs every Friday, 8am-9:00 AM,
starting June 1, 1997, ending December 31, 1997.
BEGIN:VTIMEZONE
TZID:US-Eastern
LAST-MODIFIED:19870101T000000Z
BEGIN:STANDARD
DTSTART:19971026T020000
RDATE:19971026T020000
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19971026T020000
Dawson & Stenerson Standards Track [Page 65]RFC 2445 iCalendar November 1998
RDATE:19970406T020000
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE
This is a simple example showing the current time zone rules for the
Eastern United States using a RRULE recurrence pattern. Note that
there is no effective end date to either of the Standard Time or
Daylight Time rules. This information would be valid for a recurring
event starting today and continuing indefinitely.
BEGIN:VTIMEZONE
TZID:US-Eastern
LAST-MODIFIED:19870101T000000Z
TZURL:http://zones.stds_r_us.net/tz/US-Eastern
BEGIN:STANDARD
DTSTART:19671029T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19870405T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE
This is an example showing a fictitious set of rules for the Eastern
United States, where the Daylight Time rule has an effective end date
(i.e., after that date, Daylight Time is no longer observed).
BEGIN:VTIMEZONE
TZID:US--Fictitious-Eastern
LAST-MODIFIED:19870101T000000Z
BEGIN:STANDARD
DTSTART:19671029T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
Dawson & Stenerson Standards Track [Page 66]RFC 2445 iCalendar November 1998
BEGIN:DAYLIGHT
DTSTART:19870405T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE
This is an example showing a fictitious set of rules for the Eastern
United States, where the first Daylight Time rule has an effective
end date. There is a second Daylight Time rule that picks up where
the other left off.
BEGIN:VTIMEZONE
TZID:US--Fictitious-Eastern
LAST-MODIFIED:19870101T000000Z
BEGIN:STANDARD
DTSTART:19671029T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19870405T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4;UNTIL=19980404T070000Z
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
BEGIN:DAYLIGHT
DTSTART:19990424T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=4
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE
4.6.6 Alarm Component
Component Name: VALARM
Purpose: Provide a grouping of component properties that define an
alarm.
Dawson & Stenerson Standards Track [Page 67]RFC 2445 iCalendar November 1998
Formal Definition: A "VALARM" calendar component is defined by the
following notation:
alarmc = "BEGIN" ":" "VALARM" CRLF
(audioprop / dispprop / emailprop / procprop)
"END" ":" "VALARM" CRLF
audioprop = 2*(
; 'action' and 'trigger' are both REQUIRED,
; but MUST NOT occur more than once
action / trigger /
; 'duration' and 'repeat' are both optional,
; and MUST NOT occur more than once each,
; but if one occurs, so MUST the other
duration / repeat /
; the following is optional,
; but MUST NOT occur more than once
attach /
; the following is optional,
; and MAY occur more than once
x-prop
)
dispprop = 3*(
; the following are all REQUIRED,
; but MUST NOT occur more than once
action / description / trigger /
; 'duration' and 'repeat' are both optional,
; and MUST NOT occur more than once each,
; but if one occurs, so MUST the other
duration / repeat /
; the following is optional,
Dawson & Stenerson Standards Track [Page 68]RFC 2445 iCalendar November 1998
; and MAY occur more than once
*x-prop
)
emailprop = 5*(
; the following are all REQUIRED,
; but MUST NOT occur more than once
action / description / trigger / summary
; the following is REQUIRED,
; and MAY occur more than once
attendee /
; 'duration' and 'repeat' are both optional,
; and MUST NOT occur more than once each,
; but if one occurs, so MUST the other
duration / repeat /
; the following are optional,
; and MAY occur more than once
attach / x-prop
)
procprop = 3*(
; the following are all REQUIRED,
; but MUST NOT occur more than once
action / attach / trigger /
; 'duration' and 'repeat' are both optional,
; and MUST NOT occur more than once each,
; but if one occurs, so MUST the other
duration / repeat /
Dawson & Stenerson Standards Track [Page 69]RFC 2445 iCalendar November 1998
; 'description' is optional,
; and MUST NOT occur more than once
description /
; the following is optional,
; and MAY occur more than once
x-prop
)
Description: A "VALARM" calendar component is a grouping of component
properties that is a reminder or alarm for an event or a to-do. For
example, it may be used to define a reminder for a pending event or
an overdue to-do.
The "VALARM" calendar component MUST include the "ACTION" and
"TRIGGER" properties. The "ACTION" property further constrains the
"VALARM" calendar component in the following ways:
When the action is "AUDIO", the alarm can also include one and only
one "ATTACH" property, which MUST point to a sound resource, which is
rendered when the alarm is triggered.
When the action is "DISPLAY", the alarm MUST also include a
"DESCRIPTION" property, which contains the text to be displayed when
the alarm is triggered.
When the action is "EMAIL", the alarm MUST include a "DESCRIPTION"
property, which contains the text to be used as the message body, a
"SUMMARY" property, which contains the text to be used as the message
subject, and one or more "ATTENDEE" properties, which contain the
email address of attendees to receive the message. It can also
include one or more "ATTACH" properties, which are intended to be
sent as message attachments. When the alarm is triggered, the email
message is sent.
When the action is "PROCEDURE", the alarm MUST include one and only
one "ATTACH" property, which MUST point to a procedure resource,
which is invoked when the alarm is triggered.
The "VALARM" calendar component MUST only appear within either a
"VEVENT" or "VTODO" calendar component. "VALARM" calendar components
cannot be nested. Multiple mutually independent "VALARM" calendar
components can be specified for a single "VEVENT" or "VTODO" calendar
component.
Dawson & Stenerson Standards Track [Page 70]RFC 2445 iCalendar November 1998
The "TRIGGER" property specifies when the alarm will be triggered.
The "TRIGGER" property specifies a duration prior to the start of an
event or a to-do. The "TRIGGER" edge may be explicitly set to be
relative to the "START" or "END" of the event or to-do with the
"RELATED" parameter of the "TRIGGER" property. The "TRIGGER" property
value type can alternatively be set to an absolute calendar date and
time of day value.
In an alarm set to trigger on the "START" of an event or to-do, the
"DTSTART" property MUST be present in the associated event or to-do.
In an alarm in a "VEVENT" calendar component set to trigger on the
"END" of the event, either the "DTEND" property MUST be present, or
the "DTSTART" and "DURATION" properties MUST both be present. In an
alarm in a "VTODO" calendar component set to trigger on the "END" of
the to-do, either the "DUE" property MUST be present, or the
"DTSTART" and "DURATION" properties MUST both be present.
The alarm can be defined such that it triggers repeatedly. A
definition of an alarm with a repeating trigger MUST include both the
"DURATION" and "REPEAT" properties. The "DURATION" property specifies
the delay period, after which the alarm will repeat. The "REPEAT"
property specifies the number of additional repetitions that the
alarm will triggered. This repitition count is in addition to the
initial triggering of the alarm. Both of these properties MUST be
present in order to specify a repeating alarm. If one of these two
properties is absent, then the alarm will not repeat beyond the
initial trigger.
The "ACTION" property is used within the "VALARM" calendar component
to specify the type of action invoked when the alarm is triggered.
The "VALARM" properties provide enough information for a specific
action to be invoked. It is typically the responsibility of a
"Calendar User Agent" (CUA) to deliver the alarm in the specified
fashion. An "ACTION" property value of AUDIO specifies an alarm that
causes a sound to be played to alert the user; DISPLAY specifies an
alarm that causes a text message to be displayed to the user; EMAIL
specifies an alarm that causes an electronic email message to be
delivered to one or more email addresses; and PROCEDURE specifies an
alarm that causes a procedure to be executed. The "ACTION" property
MUST specify one and only one of these values.
In an AUDIO alarm, if the optional "ATTACH" property is included, it
MUST specify an audio sound resource. The intention is that the sound
will be played as the alarm effect. If an "ATTACH" property is
specified that does not refer to a sound resource, or if the
specified sound resource cannot be rendered (because its format is
unsupported, or because it cannot be retrieved), then the CUA or
other entity responsible for playing the sound may choose a fallback
Dawson & Stenerson Standards Track [Page 71]
RFC 2445 iCalendar November 1998
action, such as playing a built-in default sound, or playing no sound
at all.
In a DISPLAY alarm, the intended alarm effect is for the text value
of the "DESCRIPTION" property to be displayed to the user.
In an EMAIL alarm, the intended alarm effect is for an email message
to be composed and delivered to all the addresses specified by the
"ATTENDEE" properties in the "VALARM" calendar component. The
"DESCRIPTION" property of the "VALARM" calendar component MUST be
used as the body text of the message, and the "SUMMARY" property MUST
be used as the subject text. Any "ATTACH" properties in the "VALARM"
calendar component SHOULD be sent as attachments to the message.
In a PROCEDURE alarm, the "ATTACH" property in the "VALARM" calendar
component MUST specify a procedure or program that is intended to be
invoked as the alarm effect. If the procedure or program is in a
format that cannot be rendered, then no procedure alarm will be
invoked. If the "DESCRIPTION" property is present, its value
specifies the argument string to be passed to the procedure or
program. "Calendar User Agents" that receive an iCalendar object with
this category of alarm, can disable or allow the "Calendar User" to
disable, or otherwise ignore this type of alarm. While a very useful
alarm capability, the PROCEDURE type of alarm SHOULD be treated by
the "Calendar User Agent" as a potential security risk.
Example: The following example is for a "VALARM" calendar component
that specifies an audio alarm that will sound at a precise time and
repeat 4 more times at 15 minute intervals:
BEGIN:VALARM
TRIGGER;VALUE=DATE-TIME:19970317T133000Z
REPEAT:4
DURATION:PT15M
ACTION:AUDIO
ATTACH;FMTTYPE=audio/basic:ftp://host.com/pub/sounds/bell-01.aud
END:VALARM
The following example is for a "VALARM" calendar component that
specifies a display alarm that will trigger 30 minutes before the
scheduled start of the event or the due date/time of the to-do it is
associated with and will repeat 2 more times at 15 minute intervals:
BEGIN:VALARM
TRIGGER:-PT30M
REPEAT:2
DURATION:PT15M
ACTION:DISPLAY
Dawson & Stenerson Standards Track [Page 72]RFC 2445 iCalendar November 1998
DESCRIPTION:Breakfast meeting with executive\n
team at 8:30 AM EST.
END:VALARM
The following example is for a "VALARM" calendar component that
specifies an email alarm that will trigger 2 days before the
scheduled due date/time of a to-do it is associated with. It does not
repeat. The email has a subject, body and attachment link.
BEGIN:VALARM
TRIGGER:-P2D
ACTION:EMAIL
ATTENDEE:MAILTO:john_doe@host.com
SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
DESCRIPTION:A draft agenda needs to be sent out to the attendees
to the weekly managers meeting (MGR-LIST). Attached is a
pointer the document template for the agenda file.
ATTACH;FMTTYPE=application/binary:http://host.com/templates/agen
da.doc
END:VALARM
The following example is for a "VALARM" calendar component that
specifies a procedural alarm that will trigger at a precise date/time
and will repeat 23 more times at one hour intervals. The alarm will
invoke a procedure file.
BEGIN:VALARM
TRIGGER;VALUE=DATE-TIME:19980101T050000Z
REPEAT:23
DURATION:PT1H
ACTION:PROCEDURE
ATTACH;FMTTYPE=application/binary:ftp://host.com/novo-
procs/felizano.exe
END:VALARM
4.7 Calendar Properties
The Calendar Properties are attributes that apply to the iCalendar
object, as a whole. These properties do not appear within a calendar
component. They SHOULD be specified after the "BEGIN:VCALENDAR"
property and prior to any calendar component.
4.7.1 Calendar Scale
Property Name: CALSCALE
Purpose: This property defines the calendar scale used for the
calendar information specified in the iCalendar object.
Dawson & Stenerson Standards Track [Page 73]RFC 2445 iCalendar November 1998
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: Property can be specified in an iCalendar object. The
default value is "GREGORIAN".
Description: This memo is based on the Gregorian calendar scale. The
Gregorian calendar scale is assumed if this property is not specified
in the iCalendar object. It is expected that other calendar scales
will be defined in other specifications or by future versions of this
memo.
Format Definition: The property is defined by the following notation:
calscale = "CALSCALE" calparam ":" calvalue CRLF
calparam = *(";" xparam)
calvalue = "GREGORIAN" / iana-token
Example: The following is an example of this property:
CALSCALE:GREGORIAN
4.7.2 Method
Property Name: METHOD
Purpose: This property defines the iCalendar object method associated
with the calendar object.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in an iCalendar object.
Description: When used in a MIME message entity, the value of this
property MUST be the same as the Content-Type "method" parameter
value. This property can only appear once within the iCalendar
object. If either the "METHOD" property or the Content-Type "method"
parameter is specified, then the other MUST also be specified.
No methods are defined by this specification. This is the subject of
other specifications, such as the iCalendar Transport-independent
Dawson & Stenerson Standards Track [Page 74]RFC 2445 iCalendar November 1998
Interoperability Protocol (iTIP) defined by [ITIP].
If this property is not present in the iCalendar object, then a
scheduling transaction MUST NOT be assumed. In such cases, the
iCalendar object is merely being used to transport a snapshot of some
calendar information; without the intention of conveying a scheduling
semantic.
Format Definition: The property is defined by the following notation:
method = "METHOD" metparam ":" metvalue CRLF
metparam = *(";" xparam)
metvalue = iana-token
Example: The following is a hypothetical example of this property to
convey that the iCalendar object is a request for a meeting:
METHOD:REQUEST
4.7.3 Product Identifier
Property Name: PRODID
Purpose: This property specifies the identifier for the product that
created the iCalendar object.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property MUST be specified once in an iCalendar
object.
Description: The vendor of the implementation SHOULD assure that this
is a globally unique identifier; using some technique such as an FPI
value, as defined in [ISO 9070].
This property SHOULD not be used to alter the interpretation of an
iCalendar object beyond the semantics specified in this memo. For
example, it is not to be used to further the understanding of non-
standard properties.
Format Definition: The property is defined by the following notation:
prodid = "PRODID" pidparam ":" pidvalue CRLF
Dawson & Stenerson Standards Track [Page 75]RFC 2445 iCalendar November 1998
pidparam = *(";" xparam)
pidvalue = text
;Any text that describes the product and version
;and that is generally assured of being unique.
Example: The following is an example of this property. It does not
imply that English is the default language.
PRODID:-//ABC Corporation//NONSGML My Product//EN
4.7.4 Version
Property Name: VERSION
Purpose: This property specifies the identifier corresponding to the
highest version number or the minimum and maximum range of the
iCalendar specification that is required in order to interpret the
iCalendar object.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property MUST be specified by an iCalendar object,
but MUST only be specified once.
Description: A value of "2.0" corresponds to this memo.
Format Definition: The property is defined by the following notation:
version = "VERSION" verparam ":" vervalue CRLF
verparam = *(";" xparam)
vervalue = "2.0" ;This memo
/ maxver
/ (minver ";" maxver)
minver = <A IANA registered iCalendar version identifier>
;Minimum iCalendar version needed to parse the iCalendar object
maxver = <A IANA registered iCalendar version identifier>
;Maximum iCalendar version needed to parse the iCalendar object
Example: The following is an example of this property:
Dawson & Stenerson Standards Track [Page 76]RFC 2445 iCalendar November 1998
VERSION:2.0
4.8 Component Properties
The following properties can appear within calendar components, as
specified by each component property definition.
4.8.1 Descriptive Component Properties
The following properties specify descriptive information about
calendar components.
4.8.1.1 Attachment
Property Name: ATTACH
Purpose: The property provides the capability to associate a document
object with a calendar component.
Value Type: The default value type for this property is URI. The
value type can also be set to BINARY to indicate inline binary
encoded content information.
Property Parameters: Non-standard, inline encoding, format type and
value data type property parameters can be specified on this
property.
Conformance: The property can be specified in a "VEVENT", "VTODO",
"VJOURNAL" or "VALARM" calendar components.
Description: The property can be specified within "VEVENT", "VTODO",
"VJOURNAL", or "VALARM" calendar components. This property can be
specified multiple times within an iCalendar object.
Format Definition: The property is defined by the following notation:
attach = "ATTACH" attparam ":" uri CRLF
attach =/ "ATTACH" attparam ";" "ENCODING" "=" "BASE64"
";" "VALUE" "=" "BINARY" ":" binary
attparam = *(
; the following is optional,
; but MUST NOT occur more than once
(";" fmttypeparam) /
Dawson & Stenerson Standards Track [Page 77]RFC 2445 iCalendar November 1998
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following are examples of this property:
ATTACH:CID:jsmith.part3.960817T083000.xyzMail@host1.com
ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
reports/r-960812.ps
4.8.1.2 Categories
Property Name: CATEGORIES
Purpose: This property defines the categories for a calendar
component.
Value Type: TEXT
Property Parameters: Non-standard and language property parameters
can be specified on this property.
Conformance: The property can be specified within "VEVENT", "VTODO"
or "VJOURNAL" calendar components.
Description: This property is used to specify categories or subtypes
of the calendar component. The categories are useful in searching for
a calendar component of a particular type and category. Within the
"VEVENT", "VTODO" or "VJOURNAL" calendar components, more than one
category can be specified as a list of categories separated by the
COMMA character (US-ASCII decimal 44).
Format Definition: The property is defined by the following notation:
categories = "CATEGORIES" catparam ":" text *("," text)
CRLF
catparam = *(
; the following is optional,
; but MUST NOT occur more than once
(";" languageparam ) /
Dawson & Stenerson Standards Track [Page 78]RFC 2445 iCalendar November 1998
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following are examples of this property:
CATEGORIES:APPOINTMENT,EDUCATION
CATEGORIES:MEETING
4.8.1.3 Classification
Property Name: CLASS
Purpose: This property defines the access classification for a
calendar component.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified once in a "VEVENT",
"VTODO" or "VJOURNAL" calendar components.
Description: An access classification is only one component of the
general security system within a calendar application. It provides a
method of capturing the scope of the access the calendar owner
intends for information within an individual calendar entry. The
access classification of an individual iCalendar component is useful
when measured along with the other security components of a calendar
system (e.g., calendar user authentication, authorization, access
rights, access role, etc.). Hence, the semantics of the individual
access classifications cannot be completely defined by this memo
alone. Additionally, due to the "blind" nature of most exchange
processes using this memo, these access classifications cannot serve
as an enforcement statement for a system receiving an iCalendar
object. Rather, they provide a method for capturing the intention of
the calendar owner for the access to the calendar component.
Format Definition: The property is defined by the following notation:
class = "CLASS" classparam ":" classvalue CRLF
classparam = *(";" xparam)
Dawson & Stenerson Standards Track [Page 79]RFC 2445 iCalendar November 1998
classvalue = "PUBLIC" / "PRIVATE" / "CONFIDENTIAL" / iana-token
/ x-name
;Default is PUBLIC
Example: The following is an example of this property:
CLASS:PUBLIC
4.8.1.4 Comment
Property Name: COMMENT
Purpose: This property specifies non-processing information intended
to provide a comment to the calendar user.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: This property can be specified in "VEVENT", "VTODO",
"VJOURNAL", "VTIMEZONE" or "VFREEBUSY" calendar components.
Description: The property can be specified multiple times.
Format Definition: The property is defined by the following notation:
comment = "COMMENT" commparam ":" text CRLF
commparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following is an example of this property:
COMMENT:The meeting really needs to include both ourselves
and the customer. We can't hold this meeting without them.
As a matter of fact\, the venue for the meeting ought to be at
Dawson & Stenerson Standards Track [Page 80]RFC 2445 iCalendar November 1998
their site. - - John
The data type for this property is TEXT.
4.8.1.5 Description
Property Name: DESCRIPTION
Purpose: This property provides a more complete description of the
calendar component, than that provided by the "SUMMARY" property.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: The property can be specified in the "VEVENT", "VTODO",
"VJOURNAL" or "VALARM" calendar components. The property can be
specified multiple times only within a "VJOURNAL" calendar component.
Description: This property is used in the "VEVENT" and "VTODO" to
capture lengthy textual decriptions associated with the activity.
This property is used in the "VJOURNAL" calendar component to capture
one more textual journal entries.
This property is used in the "VALARM" calendar component to capture
the display text for a DISPLAY category of alarm, to capture the body
text for an EMAIL category of alarm and to capture the argument
string for a PROCEDURE category of alarm.
Format Definition: The property is defined by the following notation:
description = "DESCRIPTION" descparam ":" text CRLF
descparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Dawson & Stenerson Standards Track [Page 81]RFC 2445 iCalendar November 1998
Example: The following is an example of the property with formatted
line breaks in the property value:
DESCRIPTION:Meeting to provide technical review for "Phoenix"
design.\n Happy Face Conference Room. Phoenix design team
MUST attend this meeting.\n RSVP to team leader.
The following is an example of the property with folding of long
lines:
DESCRIPTION:Last draft of the new novel is to be completed
for the editor's proof today.
4.8.1.6 Geographic Position
Property Name: GEO
Purpose: This property specifies information related to the global
position for the activity specified by a calendar component.
Value Type: FLOAT. The value MUST be two SEMICOLON separated FLOAT
values.
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in "VEVENT" or "VTODO"
calendar components.
Description: The property value specifies latitude and longitude, in
that order (i.e., "LAT LON" ordering). The longitude represents the
location east or west of the prime meridian as a positive or negative
real number, respectively. The longitude and latitude values MAY be
specified up to six decimal places, which will allow for accuracy to
within one meter of geographical position. Receiving applications
MUST accept values of this precision and MAY truncate values of
greater precision.
Values for latitude and longitude shall be expressed as decimal
fractions of degrees. Whole degrees of latitude shall be represented
by a two-digit decimal number ranging from 0 through 90. Whole
degrees of longitude shall be represented by a decimal number ranging
from 0 through 180. When a decimal fraction of a degree is specified,
it shall be separated from the whole number of degrees by a decimal
point.
Dawson & Stenerson Standards Track [Page 82]RFC 2445 iCalendar November 1998
Latitudes north of the equator shall be specified by a plus sign (+),
or by the absence of a minus sign (-), preceding the digits
designating degrees. Latitudes south of the Equator shall be
designated by a minus sign (-) preceding the digits designating
degrees. A point on the Equator shall be assigned to the Northern
Hemisphere.
Longitudes east of the prime meridian shall be specified by a plus
sign (+), or by the absence of a minus sign (-), preceding the digits
designating degrees. Longitudes west of the meridian shall be
designated by minus sign (-) preceding the digits designating
degrees. A point on the prime meridian shall be assigned to the
Eastern Hemisphere. A point on the 180th meridian shall be assigned
to the Western Hemisphere. One exception to this last convention is
permitted. For the special condition of describing a band of latitude
around the earth, the East Bounding Coordinate data element shall be
assigned the value +180 (180) degrees.
Any spatial address with a latitude of +90 (90) or -90 degrees will
specify the position at the North or South Pole, respectively. The
component for longitude may have any legal value.
With the exception of the special condition described above, this
form is specified in Department of Commerce, 1986, Representation of
geographic point locations for information interchange (Federal
Information Processing Standard 70-1): Washington, Department of
Commerce, National Institute of Standards and Technology.
The simple formula for converting degrees-minutes-seconds into
decimal degrees is:
decimal = degrees + minutes/60 + seconds/3600.
Format Definition: The property is defined by the following notation:
geo = "GEO" geoparam ":" geovalue CRLF
geoparam = *(";" xparam)
geovalue = float ";" float
;Latitude and Longitude components
Example: The following is an example of this property:
GEO:37.386013;-122.082932
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4.8.1.7 Location
Property Name: LOCATION
Purpose: The property defines the intended venue for the activity
defined by a calendar component.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: This property can be specified in "VEVENT" or "VTODO"
calendar component.
Description: Specific venues such as conference or meeting rooms may
be explicitly specified using this property. An alternate
representation may be specified that is a URI that points to
directory information with more structured specification of the
location. For example, the alternate representation may specify
either an LDAP URI pointing to an LDAP server entry or a CID URI
pointing to a MIME body part containing a vCard [RFC 2426] for the
location.
Format Definition: The property is defined by the following notation:
location = "LOCATION locparam ":" text CRLF
locparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following are some examples of this property:
LOCATION:Conference Room - F123, Bldg. 002
LOCATION;ALTREP="http://xyzcorp.com/conf-rooms/f123.vcf":
Conference Room - F123, Bldg. 002
Dawson & Stenerson Standards Track [Page 84]RFC 2445 iCalendar November 1998
4.8.1.8 Percent Complete
Property Name: PERCENT-COMPLETE
Purpose: This property is used by an assignee or delegatee of a to-do
to convey the percent completion of a to-do to the Organizer.
Value Type: INTEGER
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in a "VTODO" calendar
component.
Description: The property value is a positive integer between zero
and one hundred. A value of "0" indicates the to-do has not yet been
started. A value of "100" indicates that the to-do has been
completed. Integer values in between indicate the percent partially
complete.
When a to-do is assigned to multiple individuals, the property value
indicates the percent complete for that portion of the to-do assigned
to the assignee or delegatee. For example, if a to-do is assigned to
both individuals "A" and "B". A reply from "A" with a percent
complete of "70" indicates that "A" has completed 70% of the to-do
assigned to them. A reply from "B" with a percent complete of "50"
indicates "B" has completed 50% of the to-do assigned to them.
Format Definition: The property is defined by the following notation:
percent = "PERCENT-COMPLETE" pctparam ":" integer CRLF
pctparam = *(";" xparam)
Example: The following is an example of this property to show 39%
completion:
PERCENT-COMPLETE:39
4.8.1.9 Priority
Property Name: PRIORITY
Purpose: The property defines the relative priority for a calendar
component.
Value Type: INTEGER
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Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in a "VEVENT" or "VTODO"
calendar component.
Description: The priority is specified as an integer in the range
zero to nine. A value of zero (US-ASCII decimal 48) specifies an
undefined priority. A value of one (US-ASCII decimal 49) is the
highest priority. A value of two (US-ASCII decimal 50) is the second
highest priority. Subsequent numbers specify a decreasing ordinal
priority. A value of nine (US-ASCII decimal 58) is the lowest
priority.
A CUA with a three-level priority scheme of "HIGH", "MEDIUM" and
"LOW" is mapped into this property such that a property value in the
range of one (US-ASCII decimal 49) to four (US-ASCII decimal 52)
specifies "HIGH" priority. A value of five (US-ASCII decimal 53) is
the normal or "MEDIUM" priority. A value in the range of six (US-
ASCII decimal 54) to nine (US-ASCII decimal 58) is "LOW" priority.
A CUA with a priority schema of "A1", "A2", "A3", "B1", "B2", ...,
"C3" is mapped into this property such that a property value of one
(US-ASCII decimal 49) specifies "A1", a property value of two (US-
ASCII decimal 50) specifies "A2", a property value of three (US-ASCII
decimal 51) specifies "A3", and so forth up to a property value of 9
(US-ASCII decimal 58) specifies "C3".
Other integer values are reserved for future use.
Within a "VEVENT" calendar component, this property specifies a
priority for the event. This property may be useful when more than
one event is scheduled for a given time period.
Within a "VTODO" calendar component, this property specified a
priority for the to-do. This property is useful in prioritizing
multiple action items for a given time period.
Format Definition: The property is specified by the following
notation:
priority = "PRIORITY" prioparam ":" privalue CRLF
;Default is zero
prioparam = *(";" xparam)
privalue = integer ;Must be in the range [0..9]
; All other values are reserved for future use
Dawson & Stenerson Standards Track [Page 86]RFC 2445 iCalendar November 1998
The following is an example of a property with the highest priority:
PRIORITY:1
The following is an example of a property with a next highest
priority:
PRIORITY:2
Example: The following is an example of a property with no priority.
This is equivalent to not specifying the "PRIORITY" property:
PRIORITY:0
4.8.1.10 Resources
Property Name: RESOURCES
Purpose: This property defines the equipment or resources anticipated
for an activity specified by a calendar entity..
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: This property can be specified in "VEVENT" or "VTODO"
calendar component.
Description: The property value is an arbitrary text. More than one
resource can be specified as a list of resources separated by the
COMMA character (US-ASCII decimal 44).
Format Definition: The property is defined by the following notation:
resources = "RESOURCES" resrcparam ":" text *("," text) CRLF
resrcparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
Dawson & Stenerson Standards Track [Page 87]RFC 2445 iCalendar November 1998
(";" xparam)
)
Example: The following is an example of this property:
RESOURCES:EASEL,PROJECTOR,VCR
RESOURCES;LANGUAGE=fr:1 raton-laveur
4.8.1.11 Status
Property Name: STATUS
Purpose: This property defines the overall status or confirmation for
the calendar component.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in "VEVENT", "VTODO" or
"VJOURNAL" calendar components.
Description: In a group scheduled calendar component, the property is
used by the "Organizer" to provide a confirmation of the event to the
"Attendees". For example in a "VEVENT" calendar component, the
"Organizer" can indicate that a meeting is tentative, confirmed or
cancelled. In a "VTODO" calendar component, the "Organizer" can
indicate that an action item needs action, is completed, is in
process or being worked on, or has been cancelled. In a "VJOURNAL"
calendar component, the "Organizer" can indicate that a journal entry
is draft, final or has been cancelled or removed.
Format Definition: The property is defined by the following notation:
status = "STATUS" statparam] ":" statvalue CRLF
statparam = *(";" xparam)
statvalue = "TENTATIVE" ;Indicates event is
;tentative.
/ "CONFIRMED" ;Indicates event is
;definite.
/ "CANCELLED" ;Indicates event was
;cancelled.
;Status values for a "VEVENT"
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statvalue =/ "NEEDS-ACTION" ;Indicates to-do needs action.
/ "COMPLETED" ;Indicates to-do completed.
/ "IN-PROCESS" ;Indicates to-do in process of
/ "CANCELLED" ;Indicates to-do was cancelled.
;Status values for "VTODO".
statvalue =/ "DRAFT" ;Indicates journal is draft.
/ "FINAL" ;Indicates journal is final.
/ "CANCELLED" ;Indicates journal is removed.
;Status values for "VJOURNAL".
Example: The following is an example of this property for a "VEVENT"
calendar component:
STATUS:TENTATIVE
The following is an example of this property for a "VTODO" calendar
component:
STATUS:NEEDS-ACTION
The following is an example of this property for a "VJOURNAL"
calendar component:
STATUS:DRAFT
4.8.1.12 Summary
Property Name: SUMMARY
Purpose: This property defines a short summary or subject for the
calendar component.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: The property can be specified in "VEVENT", "VTODO",
"VJOURNAL" or "VALARM" calendar components.
Description: This property is used in the "VEVENT", "VTODO" and
"VJOURNAL" calendar components to capture a short, one line summary
about the activity or journal entry.
This property is used in the "VALARM" calendar component to capture
the subject of an EMAIL category of alarm.
Dawson & Stenerson Standards Track [Page 89]RFC 2445 iCalendar November 1998
Format Definition: The property is defined by the following notation:
summary = "SUMMARY" summparam ":" text CRLF
summparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following is an example of this property:
SUMMARY:Department Party
4.8.2 Date and Time Component Properties
The following properties specify date and time related information in
calendar components.
4.8.2.1 Date/Time Completed
Property Name: COMPLETED
Purpose: This property defines the date and time that a to-do was
actually completed.
Value Type: DATE-TIME
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in a "VTODO" calendar
component.
Description: The date and time MUST be in a UTC format.
Format Definition: The property is defined by the following notation:
completed = "COMPLETED" compparam ":" date-time CRLF
Dawson & Stenerson Standards Track [Page 90]RFC 2445 iCalendar November 1998
compparam = *(";" xparam)
Example: The following is an example of this property:
COMPLETED:19960401T235959Z
4.8.2.2 Date/Time End
Property Name: DTEND
Purpose: This property specifies the date and time that a calendar
component ends.
Value Type: The default value type is DATE-TIME. The value type can
be set to a DATE value type.
Property Parameters: Non-standard, value data type, time zone
identifier property parameters can be specified on this property.
Conformance: This property can be specified in "VEVENT" or
"VFREEBUSY" calendar components.
Description: Within the "VEVENT" calendar component, this property
defines the date and time by which the event ends. The value MUST be
later in time than the value of the "DTSTART" property.
Within the "VFREEBUSY" calendar component, this property defines the
end date and time for the free or busy time information. The time
MUST be specified in the UTC time format. The value MUST be later in
time than the value of the "DTSTART" property.
Format Definition: The property is defined by the following notation:
dtend = "DTEND" dtendparam":" dtendval CRLF
dtendparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
(";" tzidparam) /
; the following is optional,
; and MAY occur more than once
Dawson & Stenerson Standards Track [Page 91]RFC 2445 iCalendar November 1998
(";" xparam)
)
dtendval = date-time / date
;Value MUST match value type
Example: The following is an example of this property:
DTEND:19960401T235959Z
DTEND;VALUE=DATE:19980704
4.8.2.3 Date/Time Due
Property Name: DUE
Purpose: This property defines the date and time that a to-do is
expected to be completed.
Value Type: The default value type is DATE-TIME. The value type can
be set to a DATE value type.
Property Parameters: Non-standard, value data type, time zone
identifier property parameters can be specified on this property.
Conformance: The property can be specified once in a "VTODO" calendar
component.
Description: The value MUST be a date/time equal to or after the
DTSTART value, if specified.
Format Definition: The property is defined by the following notation:
due = "DUE" dueparam":" dueval CRLF
dueparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
(";" tzidparam) /
; the following is optional,
; and MAY occur more than once
Dawson & Stenerson Standards Track [Page 92]RFC 2445 iCalendar November 1998
*(";" xparam)
)
dueval = date-time / date
;Value MUST match value type
Example: The following is an example of this property:
DUE:19980430T235959Z
4.8.2.4 Date/Time Start
Property Name: DTSTART
Purpose: This property specifies when the calendar component begins.
Value Type: The default value type is DATE-TIME. The time value MUST
be one of the forms defined for the DATE-TIME value type. The value
type can be set to a DATE value type.
Property Parameters: Non-standard, value data type, time zone
identifier property parameters can be specified on this property.
Conformance: This property can be specified in the "VEVENT", "VTODO",
"VFREEBUSY", or "VTIMEZONE" calendar components.
Description: Within the "VEVENT" calendar component, this property
defines the start date and time for the event. The property is
REQUIRED in "VEVENT" calendar components. Events can have a start
date/time but no end date/time. In that case, the event does not take
up any time.
Within the "VFREEBUSY" calendar component, this property defines the
start date and time for the free or busy time information. The time
MUST be specified in UTC time.
Within the "VTIMEZONE" calendar component, this property defines the
effective start date and time for a time zone specification. This
property is REQUIRED within each STANDARD and DAYLIGHT part included
in "VTIMEZONE" calendar components and MUST be specified as a local
DATE-TIME without the "TZID" property parameter.
Format Definition: The property is defined by the following notation:
dtstart = "DTSTART" dtstparam ":" dtstval CRLF
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dtstparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
(";" tzidparam) /
; the following is optional,
; and MAY occur more than once
*(";" xparam)
)
dtstval = date-time / date
;Value MUST match value type
Example: The following is an example of this property:
DTSTART:19980118T073000Z
4.8.2.5 Duration
Property Name: DURATION
Purpose: The property specifies a positive duration of time.
Value Type: DURATION
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in "VEVENT", "VTODO",
"VFREEBUSY" or "VALARM" calendar components.
Description: In a "VEVENT" calendar component the property may be
used to specify a duration of the event, instead of an explicit end
date/time. In a "VTODO" calendar component the property may be used
to specify a duration for the to-do, instead of an explicit due
date/time. In a "VFREEBUSY" calendar component the property may be
used to specify the interval of free time being requested. In a
"VALARM" calendar component the property may be used to specify the
delay period prior to repeating an alarm.
Format Definition: The property is defined by the following notation:
Dawson & Stenerson Standards Track [Page 94]RFC 2445 iCalendar November 1998
duration = "DURATION" durparam ":" dur-value CRLF
;consisting of a positive duration of time.
durparam = *(";" xparam)
Example: The following is an example of this property that specifies
an interval of time of 1 hour and zero minutes and zero seconds:
DURATION:PT1H0M0S
The following is an example of this property that specifies an
interval of time of 15 minutes.
DURATION:PT15M
4.8.2.6 Free/Busy Time
Property Name: FREEBUSY
Purpose: The property defines one or more free or busy time
intervals.
Value Type: PERIOD. The date and time values MUST be in an UTC time
format.
Property Parameters: Non-standard or free/busy time type property
parameters can be specified on this property.
Conformance: The property can be specified in a "VFREEBUSY" calendar
component.
Property Parameter: "FBTYPE" and non-standard parameters can be
specified on this property.
Description: These time periods can be specified as either a start
and end date-time or a start date-time and duration. The date and
time MUST be a UTC time format.
"FREEBUSY" properties within the "VFREEBUSY" calendar component
SHOULD be sorted in ascending order, based on start time and then end
time, with the earliest periods first.
The "FREEBUSY" property can specify more than one value, separated by
the COMMA character (US-ASCII decimal 44). In such cases, the
"FREEBUSY" property values SHOULD all be of the same "FBTYPE"
property parameter type (e.g., all values of a particular "FBTYPE"
listed together in a single property).
Dawson & Stenerson Standards Track [Page 95]RFC 2445 iCalendar November 1998
Format Definition: The property is defined by the following notation:
freebusy = "FREEBUSY" fbparam ":" fbvalue
CRLF
fbparam = *(
; the following is optional,
; but MUST NOT occur more than once
(";" fbtypeparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
fbvalue = period *["," period]
;Time value MUST be in the UTC time format.
Example: The following are some examples of this property:
FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:19970308T160000Z/PT8H30M
FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H
FREEBUSY;FBTYPE=FREE:19970308T160000Z/PT3H,19970308T200000Z/PT1H,
19970308T230000Z/19970309T000000Z
4.8.2.7 Time Transparency
Property Name: TRANSP
Purpose: This property defines whether an event is transparent or not
to busy time searches.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified once in a "VEVENT"
calendar component.
Description: Time Transparency is the characteristic of an event that
determines whether it appears to consume time on a calendar. Events
that consume actual time for the individual or resource associated
Dawson & Stenerson Standards Track [Page 96]RFC 2445 iCalendar November 1998
with the calendar SHOULD be recorded as OPAQUE, allowing them to be
detected by free-busy time searches. Other events, which do not take
up the individual's (or resource's) time SHOULD be recorded as
TRANSPARENT, making them invisible to free-busy time searches.
Format Definition: The property is specified by the following
notation:
transp = "TRANSP" tranparam ":" transvalue CRLF
tranparam = *(";" xparam)
transvalue = "OPAQUE" ;Blocks or opaque on busy time searches.
/ "TRANSPARENT" ;Transparent on busy time searches.
;Default value is OPAQUE
Example: The following is an example of this property for an event
that is transparent or does not block on free/busy time searches:
TRANSP:TRANSPARENT
The following is an example of this property for an event that is
opaque or blocks on free/busy time searches:
TRANSP:OPAQUE
4.8.3 Time Zone Component Properties
The following properties specify time zone information in calendar
components.
4.8.3.1 Time Zone Identifier
Property Name: TZID
Purpose: This property specifies the text value that uniquely
identifies the "VTIMEZONE" calendar component.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property MUST be specified in a "VTIMEZONE"
calendar component.
Dawson & Stenerson Standards Track [Page 97]RFC 2445 iCalendar November 1998
Description: This is the label by which a time zone calendar
component is referenced by any iCalendar properties whose data type
is either DATE-TIME or TIME and not intended to specify a UTC or a
"floating" time. The presence of the SOLIDUS character (US-ASCII
decimal 47) as a prefix, indicates that this TZID represents an
unique ID in a globally defined time zone registry (when such
registry is defined).
Note: This document does not define a naming convention for time
zone identifiers. Implementers may want to use the naming
conventions defined in existing time zone specifications such as
the public-domain Olson database [TZ]. The specification of
globally unique time zone identifiers is not addressed by this
document and is left for future study.
Format Definition: This property is defined by the following
notation:
tzid = "TZID" tzidpropparam ":" [tzidprefix] text CRLF
tzidpropparam = *(";" xparam)
;tzidprefix = "/"
; Defined previously. Just listed here for reader convenience.
Example: The following are examples of non-globally unique time zone
identifiers:
TZID:US-Eastern
TZID:California-Los_Angeles
The following is an example of a fictitious globally unique time zone
identifier:
TZID:/US-New_York-New_York
4.8.3.2 Time Zone Name
Property Name: TZNAME
Purpose: This property specifies the customary designation for a time
zone description.
Value Type: TEXT
Property Parameters: Non-standard and language property parameters
can be specified on this property.
Dawson & Stenerson Standards Track [Page 98]RFC 2445 iCalendar November 1998
Conformance: This property can be specified in a "VTIMEZONE" calendar
component.
Description: This property may be specified in multiple languages; in
order to provide for different language requirements.
Format Definition: This property is defined by the following
notation:
tzname = "TZNAME" tznparam ":" text CRLF
tznparam = *(
; the following is optional,
; but MUST NOT occur more than once
(";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following are example of this property:
TZNAME:EST
The following is an example of this property when two different
languages for the time zone name are specified:
TZNAME;LANGUAGE=en:EST
TZNAME;LANGUAGE=fr-CA:HNE
4.8.3.3 Time Zone Offset From
Property Name: TZOFFSETFROM
Purpose: This property specifies the offset which is in use prior to
this time zone observance.
Value Type: UTC-OFFSET
Property Parameters: Non-standard property parameters can be
specified on this property.
Dawson & Stenerson Standards Track [Page 99]RFC 2445 iCalendar November 1998
Conformance: This property MUST be specified in a "VTIMEZONE"
calendar component.
Description: This property specifies the offset which is in use prior
to this time observance. It is used to calculate the absolute time at
which the transition to a given observance takes place. This property
MUST only be specified in a "VTIMEZONE" calendar component. A
"VTIMEZONE" calendar component MUST include this property. The
property value is a signed numeric indicating the number of hours and
possibly minutes from UTC. Positive numbers represent time zones east
of the prime meridian, or ahead of UTC. Negative numbers represent
time zones west of the prime meridian, or behind UTC.
Format Definition: The property is defined by the following notation:
tzoffsetfrom = "TZOFFSETFROM" frmparam ":" utc-offset
CRLF
frmparam = *(";" xparam)
Example: The following are examples of this property:
TZOFFSETFROM:-0500
TZOFFSETFROM:+1345
4.8.3.4 Time Zone Offset To
Property Name: TZOFFSETTO
Purpose: This property specifies the offset which is in use in this
time zone observance.
Value Type: UTC-OFFSET
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property MUST be specified in a "VTIMEZONE"
calendar component.
Description: This property specifies the offset which is in use in
this time zone observance. It is used to calculate the absolute time
for the new observance. The property value is a signed numeric
indicating the number of hours and possibly minutes from UTC.
Positive numbers represent time zones east of the prime meridian, or
ahead of UTC. Negative numbers represent time zones west of the prime
meridian, or behind UTC.
Dawson & Stenerson Standards Track [Page 100]RFC 2445 iCalendar November 1998
Format Definition: The property is defined by the following notation:
tzoffsetto = "TZOFFSETTO" toparam ":" utc-offset CRLF
toparam = *(";" xparam)
Example: The following are examples of this property:
TZOFFSETTO:-0400
TZOFFSETTO:+1245
4.8.3.5 Time Zone URL
Property Name: TZURL
Purpose: The TZURL provides a means for a VTIMEZONE component to
point to a network location that can be used to retrieve an up-to-
date version of itself.
Value Type: URI
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in a "VTIMEZONE" calendar
component.
Description: The TZURL provides a means for a VTIMEZONE component to
point to a network location that can be used to retrieve an up-to-
date version of itself. This provides a hook to handle changes
government bodies impose upon time zone definitions. Retrieval of
this resource results in an iCalendar object containing a single
VTIMEZONE component and a METHOD property set to PUBLISH.
Format Definition: The property is defined by the following notation:
tzurl = "TZURL" tzurlparam ":" uri CRLF
tzurlparam = *(";" xparam)
Example: The following is an example of this property:
TZURL:http://timezones.r.us.net/tz/US-California-Los_Angeles
Dawson & Stenerson Standards Track [Page 101]RFC 2445 iCalendar November 1998
4.8.4 Relationship Component Properties
The following properties specify relationship information in calendar
components.
4.8.4.1 Attendee
Property Name: ATTENDEE
Purpose: The property defines an "Attendee" within a calendar
component.
Value Type: CAL-ADDRESS
Property Parameters: Non-standard, language, calendar user type,
group or list membership, participation role, participation status,
RSVP expectation, delegatee, delegator, sent by, common name or
directory entry reference property parameters can be specified on
this property.
Conformance: This property MUST be specified in an iCalendar object
that specifies a group scheduled calendar entity. This property MUST
NOT be specified in an iCalendar object when publishing the calendar
information (e.g., NOT in an iCalendar object that specifies the
publication of a calendar user's busy time, event, to-do or journal).
This property is not specified in an iCalendar object that specifies
only a time zone definition or that defines calendar entities that
are not group scheduled entities, but are entities only on a single
user's calendar.
Description: The property MUST only be specified within calendar
components to specify participants, non-participants and the chair of
a group scheduled calendar entity. The property is specified within
an "EMAIL" category of the "VALARM" calendar component to specify an
email address that is to receive the email type of iCalendar alarm.
The property parameter CN is for the common or displayable name
associated with the calendar address; ROLE, for the intended role
that the attendee will have in the calendar component; PARTSTAT, for
the status of the attendee's participation; RSVP, for indicating
whether the favor of a reply is requested; CUTYPE, to indicate the
type of calendar user; MEMBER, to indicate the groups that the
attendee belongs to; DELEGATED-TO, to indicate the calendar users
that the original request was delegated to; and DELEGATED-FROM, to
indicate whom the request was delegated from; SENT-BY, to indicate
whom is acting on behalf of the ATTENDEE; and DIR, to indicate the
URI that points to the directory information corresponding to the
attendee. These property parameters can be specified on an "ATTENDEE"
Dawson & Stenerson Standards Track [Page 102]
RFC 2445 iCalendar November 1998
property in either a "VEVENT", "VTODO" or "VJOURNAL" calendar
component. They MUST not be specified in an "ATTENDEE" property in a
"VFREEBUSY" or "VALARM" calendar component. If the LANGUAGE property
parameter is specified, the identified language applies to the CN
parameter.
A recipient delegated a request MUST inherit the RSVP and ROLE values
from the attendee that delegated the request to them.
Multiple attendees can be specified by including multiple "ATTENDEE"
properties within the calendar component.
Format Definition: The property is defined by the following notation:
attendee = "ATTENDEE" attparam ":" cal-address CRLF
attparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" cutypeparam) / (";"memberparam) /
(";" roleparam) / (";" partstatparam) /
(";" rsvpparam) / (";" deltoparam) /
(";" delfromparam) / (";" sentbyparam) /
(";"cnparam) / (";" dirparam) /
(";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following are examples of this property's use for a to-
do:
ORGANIZER:MAILTO:jsmith@host1.com
ATTENDEE;MEMBER="MAILTO:DEV-GROUP@host2.com":
MAILTO:joecool@host2.com
ATTENDEE;DELEGATED-FROM="MAILTO:immud@host3.com":
MAILTO:ildoit@host1.com
The following is an example of this property used for specifying
multiple attendees to an event:
Dawson & Stenerson Standards Track [Page 103]RFC 2445 iCalendar November 1998
ORGANIZER:MAILTO:jsmith@host1.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;CN=Henry Cabot
:MAILTO:hcabot@host2.com
ATTENDEE;ROLE=REQ-PARTICIPANT;DELEGATED-FROM="MAILTO:bob@host.com"
;PARTSTAT=ACCEPTED;CN=Jane Doe:MAILTO:jdoe@host1.com
The following is an example of this property with a URI to the
directory information associated with the attendee:
ATTENDEE;CN=John Smith;DIR="ldap://host.com:6666/o=eDABC%
20Industries,c=3DUS??(cn=3DBJim%20Dolittle)":MAILTO:jimdo@
host1.com
The following is an example of this property with "delegatee" and
"delegator" information for an event:
ORGANIZER;CN=John Smith:MAILTO:jsmith@host.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=TENTATIVE;DELEGATED-FROM=
"MAILTO:iamboss@host2.com";CN=Henry Cabot:MAILTO:hcabot@
host2.com
ATTENDEE;ROLE=NON-PARTICIPANT;PARTSTAT=DELEGATED;DELEGATED-TO=
"MAILTO:hcabot@host2.com";CN=The Big Cheese:MAILTO:iamboss
@host2.com
ATTENDEE;ROLE=REQ-PARTICIPANT;PARTSTAT=ACCEPTED;CN=Jane Doe
:MAILTO:jdoe@host1.com
Example: The following is an example of this property's use when
another calendar user is acting on behalf of the "Attendee":
ATTENDEE;SENT-BY=MAILTO:jan_doe@host1.com;CN=John Smith:MAILTO:
jsmith@host1.com
4.8.4.2 Contact
Property Name: CONTACT
Purpose: The property is used to represent contact information or
alternately a reference to contact information associated with the
calendar component.
Value Type: TEXT
Property Parameters: Non-standard, alternate text representation and
language property parameters can be specified on this property.
Conformance: The property can be specified in a "VEVENT", "VTODO",
"VJOURNAL" or "VFREEBUSY" calendar component.
Dawson & Stenerson Standards Track [Page 104]RFC 2445 iCalendar November 1998
Description: The property value consists of textual contact
information. An alternative representation for the property value can
also be specified that refers to a URI pointing to an alternate form,
such as a vCard [RFC 2426], for the contact information.
Format Definition: The property is defined by the following notation:
contact = "CONTACT" contparam ":" text CRLF
contparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" altrepparam) / (";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following is an example of this property referencing
textual contact information:
CONTACT:Jim Dolittle\, ABC Industries\, +1-919-555-1234
The following is an example of this property with an alternate
representation of a LDAP URI to a directory entry containing the
contact information:
CONTACT;ALTREP="ldap://host.com:6666/o=3DABC%20Industries\,
c=3DUS??(cn=3DBJim%20Dolittle)":Jim Dolittle\, ABC Industries\,
+1-919-555-1234
The following is an example of this property with an alternate
representation of a MIME body part containing the contact
information, such as a vCard [RFC 2426] embedded in a [MIME-DIR]
content-type:
CONTACT;ALTREP="CID=<part3.msg970930T083000SILVER@host.com>":Jim
Dolittle\, ABC Industries\, +1-919-555-1234
The following is an example of this property referencing a network
resource, such as a vCard [RFC 2426] object containing the contact
information:
Dawson & Stenerson Standards Track [Page 105]RFC 2445 iCalendar November 1998
CONTACT;ALTREP="http://host.com/pdi/jdoe.vcf":Jim
Dolittle\, ABC Industries\, +1-919-555-1234
4.8.4.3 Organizer
Property Name: ORGANIZER
Purpose: The property defines the organizer for a calendar component.
Value Type: CAL-ADDRESS
Property Parameters: Non-standard, language, common name, directory
entry reference, sent by property parameters can be specified on this
property.
Conformance: This property MUST be specified in an iCalendar object
that specifies a group scheduled calendar entity. This property MUST
be specified in an iCalendar object that specifies the publication of
a calendar user's busy time. This property MUST NOT be specified in
an iCalendar object that specifies only a time zone definition or
that defines calendar entities that are not group scheduled entities,
but are entities only on a single user's calendar.
Description: The property is specified within the "VEVENT", "VTODO",
"VJOURNAL calendar components to specify the organizer of a group
scheduled calendar entity. The property is specified within the
"VFREEBUSY" calendar component to specify the calendar user
requesting the free or busy time. When publishing a "VFREEBUSY"
calendar component, the property is used to specify the calendar that
the published busy time came from.
The property has the property parameters CN, for specifying the
common or display name associated with the "Organizer", DIR, for
specifying a pointer to the directory information associated with the
"Organizer", SENT-BY, for specifying another calendar user that is
acting on behalf of the "Organizer". The non-standard parameters may
also be specified on this property. If the LANGUAGE property
parameter is specified, the identified language applies to the CN
parameter value.
Format Definition: The property is defined by the following notation:
organizer = "ORGANIZER" orgparam ":"
cal-address CRLF
orgparam = *(
; the following are optional,
Dawson & Stenerson Standards Track [Page 106]RFC 2445 iCalendar November 1998
; but MUST NOT occur more than once
(";" cnparam) / (";" dirparam) / (";" sentbyparam) /
(";" languageparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
Example: The following is an example of this property:
ORGANIZER;CN=John Smith:MAILTO:jsmith@host1.com
The following is an example of this property with a pointer to the
directory information associated with the organizer:
ORGANIZER;CN=JohnSmith;DIR="ldap://host.com:6666/o=3DDC%20Associ
ates,c=3DUS??(cn=3DJohn%20Smith)":MAILTO:jsmith@host1.com
The following is an example of this property used by another calendar
user who is acting on behalf of the organizer, with responses
intended to be sent back to the organizer, not the other calendar
user:
ORGANIZER;SENT-BY="MAILTO:jane_doe@host.com":
MAILTO:jsmith@host1.com
4.8.4.4 Recurrence ID
Property Name: RECURRENCE-ID
Purpose: This property is used in conjunction with the "UID" and
"SEQUENCE" property to identify a specific instance of a recurring
"VEVENT", "VTODO" or "VJOURNAL" calendar component. The property
value is the effective value of the "DTSTART" property of the
recurrence instance.
Value Type: The default value type for this property is DATE-TIME.
The time format can be any of the valid forms defined for a DATE-TIME
value type. See DATE-TIME value type definition for specific
interpretations of the various forms. The value type can be set to
DATE.
Dawson & Stenerson Standards Track [Page 107]RFC 2445 iCalendar November 1998
Property Parameters: Non-standard property, value data type, time
zone identifier and recurrence identifier range parameters can be
specified on this property.
Conformance: This property can be specified in an iCalendar object
containing a recurring calendar component.
Description: The full range of calendar components specified by a
recurrence set is referenced by referring to just the "UID" property
value corresponding to the calendar component. The "RECURRENCE-ID"
property allows the reference to an individual instance within the
recurrence set.
If the value of the "DTSTART" property is a DATE type value, then the
value MUST be the calendar date for the recurrence instance.
The date/time value is set to the time when the original recurrence
instance would occur; meaning that if the intent is to change a
Friday meeting to Thursday, the date/time is still set to the
original Friday meeting.
The "RECURRENCE-ID" property is used in conjunction with the "UID"
and "SEQUENCE" property to identify a particular instance of a
recurring event, to-do or journal. For a given pair of "UID" and
"SEQUENCE" property values, the "RECURRENCE-ID" value for a
recurrence instance is fixed. When the definition of the recurrence
set for a calendar component changes, and hence the "SEQUENCE"
property value changes, the "RECURRENCE-ID" for a given recurrence
instance might also change.The "RANGE" parameter is used to specify
the effective range of recurrence instances from the instance
specified by the "RECURRENCE-ID" property value. The default value
for the range parameter is the single recurrence instance only. The
value can also be "THISANDPRIOR" to indicate a range defined by the
given recurrence instance and all prior instances or the value can be
"THISANDFUTURE" to indicate a range defined by the given recurrence
instance and all subsequent instances.
Format Definition: The property is defined by the following notation:
recurid = "RECURRENCE-ID" ridparam ":" ridval CRLF
ridparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" "VALUE" "=" ("DATE-TIME" / "DATE)) /
(";" tzidparam) / (";" rangeparam) /
Dawson & Stenerson Standards Track [Page 108]RFC 2445 iCalendar November 1998
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
ridval = date-time / date
;Value MUST match value type
Example: The following are examples of this property:
RECURRENCE-ID;VALUE=DATE:19960401
RECURRENCE-ID;RANGE=THISANDFUTURE:19960120T120000Z
4.8.4.5 Related To
Property Name: RELATED-TO
Purpose: The property is used to represent a relationship or
reference between one calendar component and another.
Value Type: TEXT
Property Parameters: Non-standard and relationship type property
parameters can be specified on this property.
Conformance: The property can be specified one or more times in the
"VEVENT", "VTODO" or "VJOURNAL" calendar components.
Description: The property value consists of the persistent, globally
unique identifier of another calendar component. This value would be
represented in a calendar component by the "UID" property.
By default, the property value points to another calendar component
that has a PARENT relationship to the referencing object. The
"RELTYPE" property parameter is used to either explicitly state the
default PARENT relationship type to the referenced calendar component
or to override the default PARENT relationship type and specify
either a CHILD or SIBLING relationship. The PARENT relationship
indicates that the calendar component is a subordinate of the
referenced calendar component. The CHILD relationship indicates that
the calendar component is a superior of the referenced calendar
component. The SIBLING relationship indicates that the calendar
component is a peer of the referenced calendar component.
Dawson & Stenerson Standards Track [Page 109]RFC 2445 iCalendar November 1998
Changes to a calendar component referenced by this property can have
an implicit impact on the related calendar component. For example, if
a group event changes its start or end date or time, then the
related, dependent events will need to have their start and end dates
changed in a corresponding way. Similarly, if a PARENT calendar
component is canceled or deleted, then there is an implied impact to
the related CHILD calendar components. This property is intended only
to provide information on the relationship of calendar components. It
is up to the target calendar system to maintain any property
implications of this relationship.
Format Definition: The property is defined by the following notation:
related = "RELATED-TO" [relparam] ":" text CRLF
relparam = *(
; the following is optional,
; but MUST NOT occur more than once
(";" reltypeparam) /
; the following is optional,
; and MAY occur more than once
(";" xparm)
)
The following is an example of this property:
RELATED-TO:<jsmith.part7.19960817T083000.xyzMail@host3.com>
RELATED-TO:<19960401-080045-4000F192713-0052@host1.com>
4.8.4.6 Uniform Resource Locator
Property Name: URL
Purpose: This property defines a Uniform Resource Locator (URL)
associated with the iCalendar object.
Value Type: URI
Property Parameters: Non-standard property parameters can be
specified on this property.
Dawson & Stenerson Standards Track [Page 110]RFC 2445 iCalendar November 1998
Conformance: This property can be specified once in the "VEVENT",
"VTODO", "VJOURNAL" or "VFREEBUSY" calendar components.
Description: This property may be used in a calendar component to
convey a location where a more dynamic rendition of the calendar
information associated with the calendar component can be found. This
memo does not attempt to standardize the form of the URI, nor the
format of the resource pointed to by the property value. If the URL
property and Content-Location MIME header are both specified, they
MUST point to the same resource.
Format Definition: The property is defined by the following notation:
url = "URL" urlparam ":" uri CRLF
urlparam = *(";" xparam)
Example: The following is an example of this property:
URL:http://abc.com/pub/calendars/jsmith/mytime.ics
4.8.4.7 Unique Identifier
Property Name: UID
Purpose: This property defines the persistent, globally unique
identifier for the calendar component.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property MUST be specified in the "VEVENT", "VTODO",
"VJOURNAL" or "VFREEBUSY" calendar components.
Description: The UID itself MUST be a globally unique identifier. The
generator of the identifier MUST guarantee that the identifier is
unique. There are several algorithms that can be used to accomplish
this. The identifier is RECOMMENDED to be the identical syntax to the
[RFC 822] addr-spec. A good method to assure uniqueness is to put the
domain name or a domain literal IP address of the host on which the
identifier was created on the right hand side of the "@", and on the
left hand side, put a combination of the current calendar date and
time of day (i.e., formatted in as a DATE-TIME value) along with some
other currently unique (perhaps sequential) identifier available on
the system (for example, a process id number). Using a date/time
value on the left hand side and a domain name or domain literal on
Dawson & Stenerson Standards Track [Page 111]RFC 2445 iCalendar November 1998
the right hand side makes it possible to guarantee uniqueness since
no two hosts should be using the same domain name or IP address at
the same time. Though other algorithms will work, it is RECOMMENDED
that the right hand side contain some domain identifier (either of
the host itself or otherwise) such that the generator of the message
identifier can guarantee the uniqueness of the left hand side within
the scope of that domain.
This is the method for correlating scheduling messages with the
referenced "VEVENT", "VTODO", or "VJOURNAL" calendar component.
The full range of calendar components specified by a recurrence set
is referenced by referring to just the "UID" property value
corresponding to the calendar component. The "RECURRENCE-ID" property
allows the reference to an individual instance within the recurrence
set.
This property is an important method for group scheduling
applications to match requests with later replies, modifications or
deletion requests. Calendaring and scheduling applications MUST
generate this property in "VEVENT", "VTODO" and "VJOURNAL" calendar
components to assure interoperability with other group scheduling
applications. This identifier is created by the calendar system that
generates an iCalendar object.
Implementations MUST be able to receive and persist values of at
least 255 characters for this property.
Format Definition: The property is defined by the following notation:
uid = "UID" uidparam ":" text CRLF
uidparam = *(";" xparam)
Example: The following is an example of this property:
UID:19960401T080045Z-4000F192713-0052@host1.com
4.8.5 Recurrence Component Properties
The following properties specify recurrence information in calendar
components.
4.8.5.1 Exception Date/Times
Property Name: EXDATE
Dawson & Stenerson Standards Track [Page 112]RFC 2445 iCalendar November 1998
Purpose: This property defines the list of date/time exceptions for a
recurring calendar component.
Value Type: The default value type for this property is DATE-TIME.
The value type can be set to DATE.
Property Parameters: Non-standard, value data type and time zone
identifier property parameters can be specified on this property.
Conformance: This property can be specified in an iCalendar object
that includes a recurring calendar component.
Description: The exception dates, if specified, are used in computing
the recurrence set. The recurrence set is the complete set of
recurrence instances for a calendar component. The recurrence set is
generated by considering the initial "DTSTART" property along with
the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
within the iCalendar object. The "DTSTART" property defines the first
instance in the recurrence set. Multiple instances of the "RRULE" and
"EXRULE" properties can also be specified to define more
sophisticated recurrence sets. The final recurrence set is generated
by gathering all of the start date-times generated by any of the
specified "RRULE" and "RDATE" properties, and then excluding any
start date and times which fall within the union of start date and
times generated by any specified "EXRULE" and "EXDATE" properties.
This implies that start date and times within exclusion related
properties (i.e., "EXDATE" and "EXRULE") take precedence over those
specified by inclusion properties (i.e., "RDATE" and "RRULE"). Where
duplicate instances are generated by the "RRULE" and "RDATE"
properties, only one recurrence is considered. Duplicate instances
are ignored.
The "EXDATE" property can be used to exclude the value specified in
"DTSTART". However, in such cases the original "DTSTART" date MUST
still be maintained by the calendaring and scheduling system because
the original "DTSTART" value has inherent usage dependencies by other
properties such as the "RECURRENCE-ID".
Format Definition: The property is defined by the following notation:
exdate = "EXDATE" exdtparam ":" exdtval *("," exdtval) CRLF
exdtparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" "VALUE" "=" ("DATE-TIME" / "DATE")) /
Dawson & Stenerson Standards Track [Page 113]RFC 2445 iCalendar November 1998
(";" tzidparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
exdtval = date-time / date
;Value MUST match value type
Example: The following is an example of this property:
EXDATE:19960402T010000Z,19960403T010000Z,19960404T010000Z
4.8.5.2 Exception Rule
Property Name: EXRULE
Purpose: This property defines a rule or repeating pattern for an
exception to a recurrence set.
Value Type: RECUR
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in "VEVENT", "VTODO" or
"VJOURNAL" calendar components.
Description: The exception rule, if specified, is used in computing
the recurrence set. The recurrence set is the complete set of
recurrence instances for a calendar component. The recurrence set is
generated by considering the initial "DTSTART" property along with
the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
within the iCalendar object. The "DTSTART" defines the first instance
in the recurrence set. Multiple instances of the "RRULE" and "EXRULE"
properties can also be specified to define more sophisticated
recurrence sets. The final recurrence set is generated by gathering
all of the start date-times generated by any of the specified "RRULE"
and "RDATE" properties, and excluding any start date and times which
fall within the union of start date and times generated by any
specified "EXRULE" and "EXDATE" properties. This implies that start
date and times within exclusion related properties (i.e., "EXDATE"
and "EXRULE") take precedence over those specified by inclusion
Dawson & Stenerson Standards Track [Page 114]RFC 2445 iCalendar November 1998
properties (i.e., "RDATE" and "RRULE"). Where duplicate instances are
generated by the "RRULE" and "RDATE" properties, only one recurrence
is considered. Duplicate instances are ignored.
The "EXRULE" property can be used to exclude the value specified in
"DTSTART". However, in such cases the original "DTSTART" date MUST
still be maintained by the calendaring and scheduling system because
the original "DTSTART" value has inherent usage dependencies by other
properties such as the "RECURRENCE-ID".
Format Definition: The property is defined by the following notation:
exrule = "EXRULE" exrparam ":" recur CRLF
exrparam = *(";" xparam)
Example: The following are examples of this property. Except every
other week, on Tuesday and Thursday for 4 occurrences:
EXRULE:FREQ=WEEKLY;COUNT=4;INTERVAL=2;BYDAY=TU,TH
Except daily for 10 occurrences:
EXRULE:FREQ=DAILY;COUNT=10
Except yearly in June and July for 8 occurrences:
EXRULE:FREQ=YEARLY;COUNT=8;BYMONTH=6,7
4.8.5.3 Recurrence Date/Times
Property Name: RDATE
Purpose: This property defines the list of date/times for a
recurrence set.
Value Type: The default value type for this property is DATE-TIME.
The value type can be set to DATE or PERIOD.
Property Parameters: Non-standard, value data type and time zone
identifier property parameters can be specified on this property.
Conformance: The property can be specified in "VEVENT", "VTODO",
"VJOURNAL" or "VTIMEZONE" calendar components.
Dawson & Stenerson Standards Track [Page 115]RFC 2445 iCalendar November 1998
Description: This property can appear along with the "RRULE" property
to define an aggregate set of repeating occurrences. When they both
appear in an iCalendar object, the recurring events are defined by
the union of occurrences defined by both the "RDATE" and "RRULE".
The recurrence dates, if specified, are used in computing the
recurrence set. The recurrence set is the complete set of recurrence
instances for a calendar component. The recurrence set is generated
by considering the initial "DTSTART" property along with the "RRULE",
"RDATE", "EXDATE" and "EXRULE" properties contained within the
iCalendar object. The "DTSTART" property defines the first instance
in the recurrence set. Multiple instances of the "RRULE" and "EXRULE"
properties can also be specified to define more sophisticated
recurrence sets. The final recurrence set is generated by gathering
all of the start date/times generated by any of the specified "RRULE"
and "RDATE" properties, and excluding any start date/times which fall
within the union of start date/times generated by any specified
"EXRULE" and "EXDATE" properties. This implies that start date/times
within exclusion related properties (i.e., "EXDATE" and "EXRULE")
take precedence over those specified by inclusion properties (i.e.,
"RDATE" and "RRULE"). Where duplicate instances are generated by the
"RRULE" and "RDATE" properties, only one recurrence is considered.
Duplicate instances are ignored.
Format Definition: The property is defined by the following notation:
rdate = "RDATE" rdtparam ":" rdtval *("," rdtval) CRLF
rdtparam = *(
; the following are optional,
; but MUST NOT occur more than once
(";" "VALUE" "=" ("DATE-TIME" / "DATE" / "PERIOD")) /
(";" tzidparam) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
rdtval = date-time / date / period
;Value MUST match value type
Example: The following are examples of this property:
Dawson & Stenerson Standards Track [Page 116]RFC 2445 iCalendar November 1998
RDATE:19970714T123000Z
RDATE;TZID=US-EASTERN:19970714T083000
RDATE;VALUE=PERIOD:19960403T020000Z/19960403T040000Z,
19960404T010000Z/PT3H
RDATE;VALUE=DATE:19970101,19970120,19970217,19970421
19970526,19970704,19970901,19971014,19971128,19971129,19971225
4.8.5.4 Recurrence Rule
Property Name: RRULE
Purpose: This property defines a rule or repeating pattern for
recurring events, to-dos, or time zone definitions.
Value Type: RECUR
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified one or more times in
recurring "VEVENT", "VTODO" and "VJOURNAL" calendar components. It
can also be specified once in each STANDARD or DAYLIGHT sub-component
of the "VTIMEZONE" calendar component.
Description: The recurrence rule, if specified, is used in computing
the recurrence set. The recurrence set is the complete set of
recurrence instances for a calendar component. The recurrence set is
generated by considering the initial "DTSTART" property along with
the "RRULE", "RDATE", "EXDATE" and "EXRULE" properties contained
within the iCalendar object. The "DTSTART" property defines the first
instance in the recurrence set. Multiple instances of the "RRULE" and
"EXRULE" properties can also be specified to define more
sophisticated recurrence sets. The final recurrence set is generated
by gathering all of the start date/times generated by any of the
specified "RRULE" and "RDATE" properties, and excluding any start
date/times which fall within the union of start date/times generated
by any specified "EXRULE" and "EXDATE" properties. This implies that
start date/times within exclusion related properties (i.e., "EXDATE"
and "EXRULE") take precedence over those specified by inclusion
properties (i.e., "RDATE" and "RRULE"). Where duplicate instances are
generated by the "RRULE" and "RDATE" properties, only one recurrence
is considered. Duplicate instances are ignored.
Dawson & Stenerson Standards Track [Page 117]RFC 2445 iCalendar November 1998
The "DTSTART" and "DTEND" property pair or "DTSTART" and "DURATION"
property pair, specified within the iCalendar object defines the
first instance of the recurrence. When used with a recurrence rule,
the "DTSTART" and "DTEND" properties MUST be specified in local time
and the appropriate set of "VTIMEZONE" calendar components MUST be
included. For detail on the usage of the "VTIMEZONE" calendar
component, see the "VTIMEZONE" calendar component definition.
Any duration associated with the iCalendar object applies to all
members of the generated recurrence set. Any modified duration for
specific recurrences MUST be explicitly specified using the "RDATE"
property.
Format Definition: This property is defined by the following
notation:
rrule = "RRULE" rrulparam ":" recur CRLF
rrulparam = *(";" xparam)
Example: All examples assume the Eastern United States time zone.
Daily for 10 occurrences:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=DAILY;COUNT=10
==> (1997 9:00 AM EDT)September 2-11
Daily until December 24, 1997:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=DAILY;UNTIL=19971224T000000Z
==> (1997 9:00 AM EDT)September 2-30;October 1-25
(1997 9:00 AM EST)October 26-31;November 1-30;December 1-23
Every other day - forever:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=DAILY;INTERVAL=2
==> (1997 9:00 AM EDT)September2,4,6,8...24,26,28,30;
October 2,4,6...20,22,24
(1997 9:00 AM EST)October 26,28,30;November 1,3,5,7...25,27,29;
Dec 1,3,...
Every 10 days, 5 occurrences:
Dawson & Stenerson Standards Track [Page 118]RFC 2445 iCalendar November 1998
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=DAILY;INTERVAL=10;COUNT=5
==> (1997 9:00 AM EDT)September 2,12,22;October 2,12
Everyday in January, for 3 years:
DTSTART;TZID=US-Eastern:19980101T090000
RRULE:FREQ=YEARLY;UNTIL=20000131T090000Z;
BYMONTH=1;BYDAY=SU,MO,TU,WE,TH,FR,SA
or
RRULE:FREQ=DAILY;UNTIL=20000131T090000Z;BYMONTH=1
==> (1998 9:00 AM EDT)January 1-31
(1999 9:00 AM EDT)January 1-31
(2000 9:00 AM EDT)January 1-31
Weekly for 10 occurrences
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=WEEKLY;COUNT=10
==> (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
(1997 9:00 AM EST)October 28;November 4
Weekly until December 24, 1997
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=WEEKLY;UNTIL=19971224T000000Z
==> (1997 9:00 AM EDT)September 2,9,16,23,30;October 7,14,21
(1997 9:00 AM EST)October 28;November 4,11,18,25;
December 2,9,16,23
Every other week - forever:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;WKST=SU
==> (1997 9:00 AM EDT)September 2,16,30;October 14
(1997 9:00 AM EST)October 28;November 11,25;December 9,23
(1998 9:00 AM EST)January 6,20;February
...
Weekly on Tuesday and Thursday for 5 weeks:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=WEEKLY;UNTIL=19971007T000000Z;WKST=SU;BYDAY=TU,TH
or
Dawson & Stenerson Standards Track [Page 119]RFC 2445 iCalendar November 1998
RRULE:FREQ=WEEKLY;COUNT=10;WKST=SU;BYDAY=TU,TH
==> (1997 9:00 AM EDT)September 2,4,9,11,16,18,23,25,30;October 2
Every other week on Monday, Wednesday and Friday until December 24,
1997, but starting on Tuesday, September 2, 1997:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;UNTIL=19971224T000000Z;WKST=SU;
BYDAY=MO,WE,FR
==> (1997 9:00 AM EDT)September 2,3,5,15,17,19,29;October
1,3,13,15,17
(1997 9:00 AM EST)October 27,29,31;November 10,12,14,24,26,28;
December 8,10,12,22
Every other week on Tuesday and Thursday, for 8 occurrences:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=8;WKST=SU;BYDAY=TU,TH
==> (1997 9:00 AM EDT)September 2,4,16,18,30;October 2,14,16
Monthly on the 1st Friday for ten occurrences:
DTSTART;TZID=US-Eastern:19970905T090000
RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR
==> (1997 9:00 AM EDT)September 5;October 3
(1997 9:00 AM EST)November 7;Dec 5
(1998 9:00 AM EST)January 2;February 6;March 6;April 3
(1998 9:00 AM EDT)May 1;June 5
Monthly on the 1st Friday until December 24, 1997:
DTSTART;TZID=US-Eastern:19970905T090000
RRULE:FREQ=MONTHLY;UNTIL=19971224T000000Z;BYDAY=1FR
==> (1997 9:00 AM EDT)September 5;October 3
(1997 9:00 AM EST)November 7;December 5
Every other month on the 1st and last Sunday of the month for 10
occurrences:
DTSTART;TZID=US-Eastern:19970907T090000
RRULE:FREQ=MONTHLY;INTERVAL=2;COUNT=10;BYDAY=1SU,-1SU
==> (1997 9:00 AM EDT)September 7,28
(1997 9:00 AM EST)November 2,30
Dawson & Stenerson Standards Track [Page 120]RFC 2445 iCalendar November 1998
(1998 9:00 AM EST)January 4,25;March 1,29
(1998 9:00 AM EDT)May 3,31
Monthly on the second to last Monday of the month for 6 months:
DTSTART;TZID=US-Eastern:19970922T090000
RRULE:FREQ=MONTHLY;COUNT=6;BYDAY=-2MO
==> (1997 9:00 AM EDT)September 22;October 20
(1997 9:00 AM EST)November 17;December 22
(1998 9:00 AM EST)January 19;February 16
Monthly on the third to the last day of the month, forever:
DTSTART;TZID=US-Eastern:19970928T090000
RRULE:FREQ=MONTHLY;BYMONTHDAY=-3
==> (1997 9:00 AM EDT)September 28
(1997 9:00 AM EST)October 29;November 28;December 29
(1998 9:00 AM EST)January 29;February 26
...
Monthly on the 2nd and 15th of the month for 10 occurrences:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=2,15
==> (1997 9:00 AM EDT)September 2,15;October 2,15
(1997 9:00 AM EST)November 2,15;December 2,15
(1998 9:00 AM EST)January 2,15
Monthly on the first and last day of the month for 10 occurrences:
DTSTART;TZID=US-Eastern:19970930T090000
RRULE:FREQ=MONTHLY;COUNT=10;BYMONTHDAY=1,-1
==> (1997 9:00 AM EDT)September 30;October 1
(1997 9:00 AM EST)October 31;November 1,30;December 1,31
(1998 9:00 AM EST)January 1,31;February 1
Every 18 months on the 10th thru 15th of the month for 10
occurrences:
DTSTART;TZID=US-Eastern:19970910T090000
RRULE:FREQ=MONTHLY;INTERVAL=18;COUNT=10;BYMONTHDAY=10,11,12,13,14,
15
==> (1997 9:00 AM EDT)September 10,11,12,13,14,15
Dawson & Stenerson Standards Track [Page 121]RFC 2445 iCalendar November 1998
(1999 9:00 AM EST)March 10,11,12,13
Every Tuesday, every other month:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=MONTHLY;INTERVAL=2;BYDAY=TU
==> (1997 9:00 AM EDT)September 2,9,16,23,30
(1997 9:00 AM EST)November 4,11,18,25
(1998 9:00 AM EST)January 6,13,20,27;March 3,10,17,24,31
...
Yearly in June and July for 10 occurrences:
DTSTART;TZID=US-Eastern:19970610T090000
RRULE:FREQ=YEARLY;COUNT=10;BYMONTH=6,7
==> (1997 9:00 AM EDT)June 10;July 10
(1998 9:00 AM EDT)June 10;July 10
(1999 9:00 AM EDT)June 10;July 10
(2000 9:00 AM EDT)June 10;July 10
(2001 9:00 AM EDT)June 10;July 10
Note: Since none of the BYDAY, BYMONTHDAY or BYYEARDAY components
are specified, the day is gotten from DTSTART
Every other year on January, February, and March for 10 occurrences:
DTSTART;TZID=US-Eastern:19970310T090000
RRULE:FREQ=YEARLY;INTERVAL=2;COUNT=10;BYMONTH=1,2,3
==> (1997 9:00 AM EST)March 10
(1999 9:00 AM EST)January 10;February 10;March 10
(2001 9:00 AM EST)January 10;February 10;March 10
(2003 9:00 AM EST)January 10;February 10;March 10
Every 3rd year on the 1st, 100th and 200th day for 10 occurrences:
DTSTART;TZID=US-Eastern:19970101T090000
RRULE:FREQ=YEARLY;INTERVAL=3;COUNT=10;BYYEARDAY=1,100,200
==> (1997 9:00 AM EST)January 1
(1997 9:00 AM EDT)April 10;July 19
(2000 9:00 AM EST)January 1
(2000 9:00 AM EDT)April 9;July 18
(2003 9:00 AM EST)January 1
(2003 9:00 AM EDT)April 10;July 19
(2006 9:00 AM EST)January 1
Every 20th Monday of the year, forever:
Dawson & Stenerson Standards Track [Page 122]RFC 2445 iCalendar November 1998
DTSTART;TZID=US-Eastern:19970519T090000
RRULE:FREQ=YEARLY;BYDAY=20MO
==> (1997 9:00 AM EDT)May 19
(1998 9:00 AM EDT)May 18
(1999 9:00 AM EDT)May 17
...
Monday of week number 20 (where the default start of the week is
Monday), forever:
DTSTART;TZID=US-Eastern:19970512T090000
RRULE:FREQ=YEARLY;BYWEEKNO=20;BYDAY=MO
==> (1997 9:00 AM EDT)May 12
(1998 9:00 AM EDT)May 11
(1999 9:00 AM EDT)May 17
...
Every Thursday in March, forever:
DTSTART;TZID=US-Eastern:19970313T090000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=TH
==> (1997 9:00 AM EST)March 13,20,27
(1998 9:00 AM EST)March 5,12,19,26
(1999 9:00 AM EST)March 4,11,18,25
...
Every Thursday, but only during June, July, and August, forever:
DTSTART;TZID=US-Eastern:19970605T090000
RRULE:FREQ=YEARLY;BYDAY=TH;BYMONTH=6,7,8
==> (1997 9:00 AM EDT)June 5,12,19,26;July 3,10,17,24,31;
August 7,14,21,28
(1998 9:00 AM EDT)June 4,11,18,25;July 2,9,16,23,30;
August 6,13,20,27
(1999 9:00 AM EDT)June 3,10,17,24;July 1,8,15,22,29;
August 5,12,19,26
...
Every Friday the 13th, forever:
DTSTART;TZID=US-Eastern:19970902T090000
EXDATE;TZID=US-Eastern:19970902T090000
RRULE:FREQ=MONTHLY;BYDAY=FR;BYMONTHDAY=13
Dawson & Stenerson Standards Track [Page 123]RFC 2445 iCalendar November 1998
==> (1998 9:00 AM EST)February 13;March 13;November 13
(1999 9:00 AM EDT)August 13
(2000 9:00 AM EDT)October 13
...
The first Saturday that follows the first Sunday of the month,
forever:
DTSTART;TZID=US-Eastern:19970913T090000
RRULE:FREQ=MONTHLY;BYDAY=SA;BYMONTHDAY=7,8,9,10,11,12,13
==> (1997 9:00 AM EDT)September 13;October 11
(1997 9:00 AM EST)November 8;December 13
(1998 9:00 AM EST)January 10;February 7;March 7
(1998 9:00 AM EDT)April 11;May 9;June 13...
...
Every four years, the first Tuesday after a Monday in November,
forever (U.S. Presidential Election day):
DTSTART;TZID=US-Eastern:19961105T090000
RRULE:FREQ=YEARLY;INTERVAL=4;BYMONTH=11;BYDAY=TU;BYMONTHDAY=2,3,4,
5,6,7,8
==> (1996 9:00 AM EST)November 5
(2000 9:00 AM EST)November 7
(2004 9:00 AM EST)November 2
...
The 3rd instance into the month of one of Tuesday, Wednesday or
Thursday, for the next 3 months:
DTSTART;TZID=US-Eastern:19970904T090000
RRULE:FREQ=MONTHLY;COUNT=3;BYDAY=TU,WE,TH;BYSETPOS=3
==> (1997 9:00 AM EDT)September 4;October 7
(1997 9:00 AM EST)November 6
The 2nd to last weekday of the month:
DTSTART;TZID=US-Eastern:19970929T090000
RRULE:FREQ=MONTHLY;BYDAY=MO,TU,WE,TH,FR;BYSETPOS=-2
==> (1997 9:00 AM EDT)September 29
(1997 9:00 AM EST)October 30;November 27;December 30
(1998 9:00 AM EST)January 29;February 26;March 30
...
Dawson & Stenerson Standards Track [Page 124]RFC 2445 iCalendar November 1998
Every 3 hours from 9:00 AM to 5:00 PM on a specific day:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=HOURLY;INTERVAL=3;UNTIL=19970902T170000Z
==> (September 2, 1997 EDT)09:00,12:00,15:00
Every 15 minutes for 6 occurrences:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=MINUTELY;INTERVAL=15;COUNT=6
==> (September 2, 1997 EDT)09:00,09:15,09:30,09:45,10:00,10:15
Every hour and a half for 4 occurrences:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=MINUTELY;INTERVAL=90;COUNT=4
==> (September 2, 1997 EDT)09:00,10:30;12:00;13:30
Every 20 minutes from 9:00 AM to 4:40 PM every day:
DTSTART;TZID=US-Eastern:19970902T090000
RRULE:FREQ=DAILY;BYHOUR=9,10,11,12,13,14,15,16;BYMINUTE=0,20,40
or
RRULE:FREQ=MINUTELY;INTERVAL=20;BYHOUR=9,10,11,12,13,14,15,16
==> (September 2, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
... 16:00,16:20,16:40
(September 3, 1997 EDT)9:00,9:20,9:40,10:00,10:20,
...16:00,16:20,16:40
...
An example where the days generated makes a difference because of
WKST:
DTSTART;TZID=US-Eastern:19970805T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=MO
==> (1997 EDT)Aug 5,10,19,24
changing only WKST from MO to SU, yields different results...
DTSTART;TZID=US-Eastern:19970805T090000
RRULE:FREQ=WEEKLY;INTERVAL=2;COUNT=4;BYDAY=TU,SU;WKST=SU
==> (1997 EDT)August 5,17,19,31
Dawson & Stenerson Standards Track [Page 125]RFC 2445 iCalendar November 1998
4.8.6 Alarm Component Properties
The following properties specify alarm information in calendar
components.
4.8.6.1 Action
Property Name: ACTION
Purpose: This property defines the action to be invoked when an alarm
is triggered.
Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property MUST be specified once in a "VALARM"
calendar component.
Description: Each "VALARM" calendar component has a particular type
of action associated with it. This property specifies the type of
action
Format Definition: The property is defined by the following notation:
action = "ACTION" actionparam ":" actionvalue CRLF
actionparam = *(";" xparam)
actionvalue = "AUDIO" / "DISPLAY" / "EMAIL" / "PROCEDURE"
/ iana-token / x-name
Example: The following are examples of this property in a "VALARM"
calendar component:
ACTION:AUDIO
ACTION:DISPLAY
ACTION:PROCEDURE
4.8.6.2 Repeat Count
Property Name: REPEAT
Purpose: This property defines the number of time the alarm should be
repeated, after the initial trigger.
Dawson & Stenerson Standards Track [Page 126]RFC 2445 iCalendar November 1998
Value Type: INTEGER
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in a "VALARM" calendar
component.
Description: If the alarm triggers more than once, then this property
MUST be specified along with the "DURATION" property.
Format Definition: The property is defined by the following notation:
repeatcnt = "REPEAT" repparam ":" integer CRLF
;Default is "0", zero.
repparam = *(";" xparam)
Example: The following is an example of this property for an alarm
that repeats 4 additional times with a 5 minute delay after the
initial triggering of the alarm:
REPEAT:4
DURATION:PT5M
4.8.6.3 Trigger
Property Name: TRIGGER
Purpose: This property specifies when an alarm will trigger.
Value Type: The default value type is DURATION. The value type can be
set to a DATE-TIME value type, in which case the value MUST specify a
UTC formatted DATE-TIME value.
Property Parameters: Non-standard, value data type, time zone
identifier or trigger relationship property parameters can be
specified on this property. The trigger relationship property
parameter MUST only be specified when the value type is DURATION.
Conformance: This property MUST be specified in the "VALARM" calendar
component.
Description: Within the "VALARM" calendar component, this property
defines when the alarm will trigger. The default value type is
DURATION, specifying a relative time for the trigger of the alarm.
The default duration is relative to the start of an event or to-do
that the alarm is associated with. The duration can be explicitly set
Dawson & Stenerson Standards Track [Page 127]RFC 2445 iCalendar November 1998
to trigger from either the end or the start of the associated event
or to-do with the "RELATED" parameter. A value of START will set the
alarm to trigger off the start of the associated event or to-do. A
value of END will set the alarm to trigger off the end of the
associated event or to-do.
Either a positive or negative duration may be specified for the
"TRIGGER" property. An alarm with a positive duration is triggered
after the associated start or end of the event or to-do. An alarm
with a negative duration is triggered before the associated start or
end of the event or to-do.
The "RELATED" property parameter is not valid if the value type of
the property is set to DATE-TIME (i.e., for an absolute date and time
alarm trigger). If a value type of DATE-TIME is specified, then the
property value MUST be specified in the UTC time format. If an
absolute trigger is specified on an alarm for a recurring event or
to-do, then the alarm will only trigger for the specified absolute
date/time, along with any specified repeating instances.
If the trigger is set relative to START, then the "DTSTART" property
MUST be present in the associated "VEVENT" or "VTODO" calendar
component. If an alarm is specified for an event with the trigger set
relative to the END, then the "DTEND" property or the "DSTART" and
"DURATION' properties MUST be present in the associated "VEVENT"
calendar component. If the alarm is specified for a to-do with a
trigger set relative to the END, then either the "DUE" property or
the "DSTART" and "DURATION' properties MUST be present in the
associated "VTODO" calendar component.
Alarms specified in an event or to-do which is defined in terms of a
DATE value type will be triggered relative to 00:00:00 UTC on the
specified date. For example, if "DTSTART:19980205, then the duration
trigger will be relative to19980205T000000Z.
Format Definition: The property is defined by the following notation:
trigger = "TRIGGER" (trigrel / trigabs)
trigrel = *(
; the following are optional,
; but MUST NOT occur more than once
(";" "VALUE" "=" "DURATION") /
(";" trigrelparam) /
; the following is optional,
Dawson & Stenerson Standards Track [Page 128]RFC 2445 iCalendar November 1998
; and MAY occur more than once
(";" xparam)
) ":" dur-value
trigabs = 1*(
; the following is REQUIRED,
; but MUST NOT occur more than once
(";" "VALUE" "=" "DATE-TIME") /
; the following is optional,
; and MAY occur more than once
(";" xparam)
) ":" date-time
Example: A trigger set 15 minutes prior to the start of the event or
to-do.
TRIGGER:-P15M
A trigger set 5 minutes after the end of the event or to-do.
TRIGGER;RELATED=END:P5M
A trigger set to an absolute date/time.
TRIGGER;VALUE=DATE-TIME:19980101T050000Z
4.8.7 Change Management Component Properties
The following properties specify change management information in
calendar components.
4.8.7.1 Date/Time Created
Property Name: CREATED
Purpose: This property specifies the date and time that the calendar
information was created by the calendar user agent in the calendar
store.
Note: This is analogous to the creation date and time for a file
in the file system.
Dawson & Stenerson Standards Track [Page 129]RFC 2445 iCalendar November 1998
Value Type: DATE-TIME
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified once in "VEVENT", "VTODO"
or "VJOURNAL" calendar components.
Description: The date and time is a UTC value.
Format Definition: The property is defined by the following notation:
created = "CREATED" creaparam ":" date-time CRLF
creaparam = *(";" xparam)
Example: The following is an example of this property:
CREATED:19960329T133000Z
4.8.7.2 Date/Time Stamp
Property Name: DTSTAMP
Purpose: The property indicates the date/time that the instance of
the iCalendar object was created.
Value Type: DATE-TIME
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property MUST be included in the "VEVENT", "VTODO",
"VJOURNAL" or "VFREEBUSY" calendar components.
Description: The value MUST be specified in the UTC time format.
This property is also useful to protocols such as [IMIP] that have
inherent latency issues with the delivery of content. This property
will assist in the proper sequencing of messages containing iCalendar
objects.
This property is different than the "CREATED" and "LAST-MODIFIED"
properties. These two properties are used to specify when the
particular calendar data in the calendar store was created and last
modified. This is different than when the iCalendar object
representation of the calendar service information was created or
last modified.
Dawson & Stenerson Standards Track [Page 130]RFC 2445 iCalendar November 1998
Format Definition: The property is defined by the following notation:
dtstamp = "DTSTAMP" stmparam ":" date-time CRLF
stmparam = *(";" xparam)
Example:
DTSTAMP:19971210T080000Z
4.8.7.3 Last Modified
Property Name: LAST-MODIFIED
Purpose: The property specifies the date and time that the
information associated with the calendar component was last revised
in the calendar store.
Note: This is analogous to the modification date and time for a
file in the file system.
Value Type: DATE-TIME
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: This property can be specified in the "EVENT", "VTODO",
"VJOURNAL" or "VTIMEZONE" calendar components.
Description: The property value MUST be specified in the UTC time
format.
Format Definition: The property is defined by the following notation:
last-mod = "LAST-MODIFIED" lstparam ":" date-time CRLF
lstparam = *(";" xparam)
Example: The following is are examples of this property:
LAST-MODIFIED:19960817T133000Z
4.8.7.4 Sequence Number
Property Name: SEQUENCE
Purpose: This property defines the revision sequence number of the
calendar component within a sequence of revisions.
Dawson & Stenerson Standards Track [Page 131]RFC 2445 iCalendar November 1998
Value Type: integer
Property Parameters: Non-standard property parameters can be
specified on this property.
Conformance: The property can be specified in "VEVENT", "VTODO" or
"VJOURNAL" calendar component.
Description: When a calendar component is created, its sequence
number is zero (US-ASCII decimal 48). It is monotonically incremented
by the "Organizer's" CUA each time the "Organizer" makes a
significant revision to the calendar component. When the "Organizer"
makes changes to one of the following properties, the sequence number
MUST be incremented:
. "DTSTART"
. "DTEND"
. "DUE"
. "RDATE"
. "RRULE"
. "EXDATE"
. "EXRULE"
. "STATUS"
In addition, changes made by the "Organizer" to other properties can
also force the sequence number to be incremented. The "Organizer" CUA
MUST increment the sequence number when ever it makes changes to
properties in the calendar component that the "Organizer" deems will
jeopardize the validity of the participation status of the
"Attendees". For example, changing the location of a meeting from one
locale to another distant locale could effectively impact the
participation status of the "Attendees".
The "Organizer" includes this property in an iCalendar object that it
sends to an "Attendee" to specify the current version of the calendar
component.
The "Attendee" includes this property in an iCalendar object that it
sends to the "Organizer" to specify the version of the calendar
component that the "Attendee" is referring to.
Dawson & Stenerson Standards Track [Page 132]RFC 2445 iCalendar November 1998
A change to the sequence number is not the mechanism that an
"Organizer" uses to request a response from the "Attendees". The
"RSVP" parameter on the "ATTENDEE" property is used by the
"Organizer" to indicate that a response from the "Attendees" is
requested.
Format Definition: This property is defined by the following
notation:
seq = "SEQUENCE" seqparam ":" integer CRLF
; Default is "0"
seqparam = *(";" xparam)
Example: The following is an example of this property for a calendar
component that was just created by the "Organizer".
SEQUENCE:0
The following is an example of this property for a calendar component
that has been revised two different times by the "Organizer".
SEQUENCE:2
4.8.8 Miscellaneous Component Properties
The following properties specify information about a number of
miscellaneous features of calendar components.
4.8.8.1 Non-standard Properties
Property Name: Any property name with a "X-" prefix
Purpose: This class of property provides a framework for defining
non-standard properties.
Value Type: TEXT
Property Parameters: Non-standard and language property parameters
can be specified on this property.
Conformance: This property can be specified in any calendar
component.
Description: The MIME Calendaring and Scheduling Content Type
provides a "standard mechanism for doing non-standard things". This
extension support is provided for implementers to "push the envelope"
on the existing version of the memo. Extension properties are
Dawson & Stenerson Standards Track [Page 133]RFC 2445 iCalendar November 1998
specified by property and/or property parameter names that have the
prefix text of "X-" (the two character sequence: LATIN CAPITAL LETTER
X character followed by the HYPEN-MINUS character). It is recommended
that vendors concatenate onto this sentinel another short prefix text
to identify the vendor. This will facilitate readability of the
extensions and minimize possible collision of names between different
vendors. User agents that support this content type are expected to
be able to parse the extension properties and property parameters but
can ignore them.
At present, there is no registration authority for names of extension
properties and property parameters. The data type for this property
is TEXT. Optionally, the data type can be any of the other valid data
types.
Format Definition: The property is defined by the following notation:
x-prop = x-name *(";" xparam) [";" languageparam] ":" text CRLF
; Lines longer than 75 octets should be folded
Example: The following might be the ABC vendor's extension for an
audio-clip form of subject property:
X-ABC-MMSUBJ;X-ABC-MMSUBJTYPE=wave:http://load.noise.org/mysubj.wav
4.8.8.2 Request Status
Property Name: REQUEST-STATUS
Purpose: This property defines the status code returned for a
scheduling request.
Value Type: TEXT
Property Parameters: Non-standard and language property parameters
can be specified on this property.
Conformance: The property can be specified in "VEVENT", "VTODO",
"VJOURNAL" or "VFREEBUSY" calendar component.
Description: This property is used to return status code information
related to the processing of an associated iCalendar object. The data
type for this property is TEXT.
The value consists of a short return status component, a longer
return status description component, and optionally a status-specific
data component. The components of the value are separated by the
SEMICOLON character (US-ASCII decimal 59).
Dawson & Stenerson Standards Track [Page 134]RFC 2445 iCalendar November 1998
The short return status is a PERIOD character (US-ASCII decimal 46)
separated 3-tuple of integers. For example, "3.1.1". The successive
levels of integers provide for a successive level of status code
granularity.
The following are initial classes for the return status code.
Individual iCalendar object methods will define specific return
status codes for these classes. In addition, other classes for the
return status code may be defined using the registration process
defined later in this memo.
|==============+===============================================|
| Short Return | Longer Return Status Description |
| Status Code | |
|==============+===============================================|
| 1.xx | Preliminary success. This class of status |
| | of status code indicates that the request has |
| | request has been initially processed but that |
| | completion is pending. |
|==============+===============================================|
| 2.xx | Successful. This class of status code |
| | indicates that the request was completed |
| | successfuly. However, the exact status code |
| | can indicate that a fallback has been taken. |
|==============+===============================================|
| 3.xx | Client Error. This class of status code |
| | indicates that the request was not successful.|
| | The error is the result of either a syntax or |
| | a semantic error in the client formatted |
| | request. Request should not be retried until |
| | the condition in the request is corrected. |
|==============+===============================================|
| 4.xx | Scheduling Error. This class of status code |
| | indicates that the request was not successful.|
| | Some sort of error occurred within the |
| | calendaring and scheduling service, not |
| | directly related to the request itself. |
|==============+===============================================|
Format Definition: The property is defined by the following notation:
rstatus = "REQUEST-STATUS" rstatparam ":"
statcode ";" statdesc [";" extdata]
rstatparam = *(
; the following is optional,
; but MUST NOT occur more than once
Dawson & Stenerson Standards Track [Page 135]RFC 2445 iCalendar November 1998
(";" languageparm) /
; the following is optional,
; and MAY occur more than once
(";" xparam)
)
statcode = 1*DIGIT *("." 1*DIGIT)
;Hierarchical, numeric return status code
statdesc = text
;Textual status description
extdata = text
;Textual exception data. For example, the offending property
;name and value or complete property line.
Example: The following are some possible examples of this property.
The COMMA and SEMICOLON separator characters in the property value
are BACKSLASH character escaped because they appear in a text value.
REQUEST-STATUS:2.0;Success
REQUEST-STATUS:3.1;Invalid property value;DTSTART:96-Apr-01
REQUEST-STATUS:2.8; Success\, repeating event ignored. Scheduled
as a single event.;RRULE:FREQ=WEEKLY\;INTERVAL=2
REQUEST-STATUS:4.1;Event conflict. Date/time is busy.
REQUEST-STATUS:3.7;Invalid calendar user;ATTENDEE:
MAILTO:jsmith@host.com
5 iCalendar Object Examples
The following examples are provided as an informational source of
illustrative iCalendar objects consistent with this content type.
The following example specifies a three-day conference that begins at
8:00 AM EDT, September 18, 1996 and end at 6:00 PM EDT, September 20,
1996.
BEGIN:VCALENDAR PRODID:-//xyz Corp//NONSGML PDA Calendar Verson
1.0//EN VERSION:2.0 BEGIN:VEVENT DTSTAMP:19960704T120000Z
UID:uid1@host.com ORGANIZER:MAILTO:jsmith@host.com
DTSTART:19960918T143000Z DTEND:19960920T220000Z STATUS:CONFIRMED
Dawson & Stenerson Standards Track [Page 136]RFC 2445 iCalendar November 1998
CATEGORIES:CONFERENCE SUMMARY:Networld+Interop Conference
DESCRIPTION:Networld+Interop Conference
and Exhibit\nAtlanta World Congress Center\n
Atlanta, Georgia END:VEVENT END:VCALENDAR
The following example specifies a group scheduled meeting that begin
at 8:30 AM EST on March 12, 1998 and end at 9:30 AM EST on March 12,
1998. The "Organizer" has scheduled the meeting with one or more
calendar users in a group. A time zone specification for Eastern
United States has been specified.
BEGIN:VCALENDAR
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:US-Eastern
BEGIN:STANDARD
DTSTART:19981025T020000
RDATE:19981025T020000
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19990404T020000
RDATE:19990404T020000
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
DTSTAMP:19980309T231000Z
UID:guid-1.host1.com
ORGANIZER;ROLE=CHAIR:MAILTO:mrbig@host.com
ATTENDEE;RSVP=TRUE;ROLE=REQ-PARTICIPANT;CUTYPE=GROUP:
MAILTO:employee-A@host.com
DESCRIPTION:Project XYZ Review Meeting
CATEGORIES:MEETING
CLASS:PUBLIC
CREATED:19980309T130000Z
SUMMARY:XYZ Project Review
DTSTART;TZID=US-Eastern:19980312T083000
DTEND;TZID=US-Eastern:19980312T093000
LOCATION:1CP Conference Room 4350
END:VEVENT
END:VCALENDAR
Dawson & Stenerson Standards Track [Page 137]RFC 2445 iCalendar November 1998
The following is an example of an iCalendar object passed in a MIME
message with a single body part consisting of a "text/calendar"
Content Type.
TO:jsmith@host1.com
FROM:jdoe@host1.com
MIME-VERSION:1.0
MESSAGE-ID:<id3@host1.com>
CONTENT-TYPE:text/calendar
BEGIN:VCALENDAR
METHOD:xyz
VERSION:2.0
PRODID:-//ABC Corporation//NONSGML My Product//EN
BEGIN:VEVENT
DTSTAMP:19970324T1200Z
SEQUENCE:0
UID:uid3@host1.com
ORGANIZER:MAILTO:jdoe@host1.com
ATTENDEE;RSVP=TRUE:MAILTO:jsmith@host1.com
DTSTART:19970324T123000Z
DTEND:19970324T210000Z
CATEGORIES:MEETING,PROJECT
CLASS:PUBLIC
SUMMARY:Calendaring Interoperability Planning Meeting
DESCRIPTION:Discuss how we can test c&s interoperability\n
using iCalendar and other IETF standards.
LOCATION:LDB Lobby
ATTACH;FMTTYPE=application/postscript:ftp://xyzCorp.com/pub/
conf/bkgrnd.ps
END:VEVENT
END:VCALENDAR
The following is an example of a to-do due on April 15, 1998. An
audio alarm has been specified to remind the calendar user at noon,
the day before the to-do is expected to be completed and repeat
hourly, four additional times. The to-do definition has been modified
twice since it was initially created.
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//ABC Corporation//NONSGML My Product//EN
BEGIN:VTODO
DTSTAMP:19980130T134500Z
SEQUENCE:2
UID:uid4@host1.com
ORGANIZER:MAILTO:unclesam@us.gov
ATTENDEE;PARTSTAT=ACCEPTED:MAILTO:jqpublic@host.com
Dawson & Stenerson Standards Track [Page 138]RFC 2445 iCalendar November 1998
DUE:19980415T235959
STATUS:NEEDS-ACTION
SUMMARY:Submit Income Taxes
BEGIN:VALARM
ACTION:AUDIO
TRIGGER:19980403T120000
ATTACH;FMTTYPE=audio/basic:http://host.com/pub/audio-
files/ssbanner.aud
REPEAT:4
DURATION:PT1H
END:VALARM
END:VTODO
END:VCALENDAR
The following is an example of a journal entry.
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//ABC Corporation//NONSGML My Product//EN
BEGIN:VJOURNAL
DTSTAMP:19970324T120000Z
UID:uid5@host1.com
ORGANIZER:MAILTO:jsmith@host.com
STATUS:DRAFT
CLASS:PUBLIC
CATEGORY:Project Report, XYZ, Weekly Meeting
DESCRIPTION:Project xyz Review Meeting Minutes\n
Agenda\n1. Review of project version 1.0 requirements.\n2.
Definition
of project processes.\n3. Review of project schedule.\n
Participants: John Smith, Jane Doe, Jim Dandy\n-It was
decided that the requirements need to be signed off by
product marketing.\n-Project processes were accepted.\n
-Project schedule needs to account for scheduled holidays
and employee vacation time. Check with HR for specific
dates.\n-New schedule will be distributed by Friday.\n-
Next weeks meeting is cancelled. No meeting until 3/23.
END:VJOURNAL
END:VCALENDAR
The following is an example of published busy time information. The
iCalendar object might be placed in the network resource
www.host.com/calendar/busytime/jsmith.ifb.
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//RDU Software//NONSGML HandCal//EN
BEGIN:VFREEBUSY
Dawson & Stenerson Standards Track [Page 139]RFC 2445 iCalendar November 1998
ORGANIZER:MAILTO:jsmith@host.com
DTSTART:19980313T141711Z
DTEND:19980410T141711Z
FREEBUSY:19980314T233000Z/19980315T003000Z
FREEBUSY:19980316T153000Z/19980316T163000Z
FREEBUSY:19980318T030000Z/19980318T040000Z
URL:http://www.host.com/calendar/busytime/jsmith.ifb
END:VFREEBUSY
END:VCALENDAR
6 Recommended Practices
These recommended practices should be followed in order to assure
consistent handling of the following cases for an iCalendar object.
1. Content lines longer than 75 octets SHOULD be folded.
2. A calendar entry with a "DTSTART" property but no "DTEND"
property does not take up any time. It is intended to represent
an event that is associated with a given calendar date and time
of day, such as an anniversary. Since the event does not take up
any time, it MUST NOT be used to record busy time no matter what
the value for the "TRANSP" property.
3. When the "DTSTART" and "DTEND", for "VEVENT", "VJOURNAL" and
"VFREEBUSY" calendar components, and "DTSTART" and "DUE", for
"VTODO" calendar components, have the same value data type (e.g.,
DATE-TIME), they SHOULD specify values in the same time format
(e.g., UTC time format).
4. When the combination of the "RRULE" and "RDATE" properties on an
iCalendar object produces multiple instances having the same
start date/time, they should be collapsed to, and considered as,
a single instance.
5. When a calendar user receives multiple requests for the same
calendar component (e.g., REQUEST for a "VEVENT" calendar
component) as a result of being on multiple mailing lists
specified by "ATTENDEE" properties in the request, they SHOULD
respond to only one of the requests. The calendar user SHOULD
also specify (using the "MEMBER" parameter of the "ATTENDEE"
property) which mailing list they are a member of.
6. An implementation can truncate a "SUMMARY" property value to 255
characters.
Dawson & Stenerson Standards Track [Page 140]RFC 2445 iCalendar November 1998
7. If seconds of the minute are not supported by an implementation,
then a value of "00" SHOULD be specified for the seconds
component in a time value.
8. If the value type parameter (VALUE=) contains an unknown value
type, it SHOULD be treated as TEXT.
9. TZURL values SHOULD NOT be specified as a FILE URI type. This URI
form can be useful within an organization, but is problematic in
the Internet.
10. Some possible English values for CATEGORIES property include
"ANNIVERSARY", "APPOINTMENT", "BUSINESS", "EDUCATION",
"HOLIDAY", "MEETING", "MISCELLANEOUS", "NON-WORKING HOURS", "NOT
IN OFFICE", "PERSONAL", "PHONE CALL", "SICK DAY", "SPECIAL
OCCASION", "TRAVEL", "VACATION". Categories can be specified in
any registered language.
11. Some possible English values for RESOURCES property include
"CATERING", "CHAIRS", "COMPUTER PROJECTOR", "EASEL", "OVERHEAD
PROJECTOR", "SPEAKER PHONE", "TABLE", "TV", "VCR", "VIDEO
PHONE", "VEHICLE". Resources can be specified in any registered
language.
7 Registration of Content Type Elements
This section provides the process for registration of MIME
Calendaring and Scheduling Content Type iCalendar object methods and
new or modified properties.
7.1 Registration of New and Modified iCalendar Object Methods
New MIME Calendaring and Scheduling Content Type iCalendar object
methods are registered by the publication of an IETF Request for
Comments (RFC). Changes to an iCalendar object method are registered
by the publication of a revision of the RFC defining the method.
7.2 Registration of New Properties
This section defines procedures by which new properties or enumerated
property values for the MIME Calendaring and Scheduling Content Type
can be registered with the IANA. Non-IANA properties can be used by
bilateral agreement, provided the associated properties names follow
the "X-" convention.
The procedures defined here are designed to allow public comment and
review of new properties, while posing only a small impediment to the
definition of new properties.
Dawson & Stenerson Standards Track [Page 141]RFC 2445 iCalendar November 1998
Registration of a new property is accomplished by the following
steps.
7.2.1 Define the property
A property is defined by completing the following template.
To: ietf-calendar@imc.org
Subject: Registration of text/calendar MIME property XXX
Property name:
Property purpose:
Property value type(s):
Property parameter (s):
Conformance:
Description:
Format definition:
Examples:
The meaning of each field in the template is as follows.
Property name: The name of the property, as it will appear in the
body of an text/calendar MIME Content-Type "property: value" line to
the left of the colon ":".
Property purpose: The purpose of the property (e.g., to indicate a
delegate for the event or to-do, etc.). Give a short but clear
description.
Property value type (s): Any of the valid value types for the
property value needs to be specified. The default value type also
needs to be specified. If a new value type is specified, it needs to
be declared in this section.
Property parameter (s): Any of the valid property parameters for the
property needs to be specified.
Conformance: The calendar components that the property can appear in
needs to be specified.
Dawson & Stenerson Standards Track [Page 142]RFC 2445 iCalendar November 1998
Description: Any special notes about the property, how it is to be
used, etc.
Format definition: The ABNF for the property definition needs to be
specified.
Examples: One or more examples of instances of the property needs to
be specified.
7.2.2 Post the Property definition
The property description MUST be posted to the new property
discussion list, ietf-calendar@imc.org.
7.2.3 Allow a comment period
Discussion on the new property MUST be allowed to take place on the
list for a minimum of two weeks. Consensus MUST be reached on the
property before proceeding to the next step.
7.2.4 Submit the property for approval
Once the two-week comment period has elapsed, and the proposer is
convinced consensus has been reached on the property, the
registration application should be submitted to the Method Reviewer
for approval. The Method Reviewer is appointed to the Application
Area Directors and can either accept or reject the property
registration. An accepted registration should be passed on by the
Method Reviewer to the IANA for inclusion in the official IANA method
registry. The registration can be rejected for any of the following
reasons. 1) Insufficient comment period; 2) Consensus not reached; 3)
Technical deficiencies raised on the list or elsewhere have not been
addressed. The Method Reviewer's decision to reject a property can be
appealed by the proposer to the IESG, or the objections raised can be
addressed by the proposer and the property resubmitted.
7.3 Property Change Control
Existing properties can be changed using the same process by which
they were registered.
1. Define the change
2. Post the change
3. Allow a comment period
4. Submit the property for approval
Dawson & Stenerson Standards Track [Page 143]RFC 2445 iCalendar November 1998
Note that the original author or any other interested party can
propose a change to an existing property, but that such changes
should only be proposed when there are serious omissions or errors in
the published memo. The Method Reviewer can object to a change if it
is not backward compatible, but is not required to do so.
Property definitions can never be deleted from the IANA registry, but
properties which are no longer believed to be useful can be declared
OBSOLETE by a change to their "intended use" field.
8 References
[IMIP] Dawson, F., Mansour, S. and S. Silverberg, "iCalendar
Message-based Interoperability Protocol (IMIP)", RFC 2447,
November 1998.
[ITIP] Silverberg, S., Mansour, S., Dawson, F. and R. Hopson,
"iCalendar Transport-Independent Interoperability Protocol
(iTIP) : Scheduling Events, Busy Time, To-dos and Journal
Entries", RFC 2446, November 1998.
[ISO 8601] ISO 8601, "Data elements and interchange formats-
Information interchange--Representation of dates and
times", International Organization for Standardization,
June, 1988.
[ISO 9070] ISO/IEC 9070, "Information Technology_SGML Support
Facilities--Registration Procedures for Public Text Owner
Identifiers", Second Edition, International Organization
for Standardization, April 1991.
[RFC 822] Crocker, D., "Standard for the Format of ARPA Internet
Text Messages", STD 11, RFC 822, August 1982.
[RFC 1738] Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
Resource Locators (URL)", RFC 1738, December 1994.
[RFC 1766] Alvestrand, H., "Tags for the Identification of
Languages", RFC 1766, March 1995.
[RFC 2045] Freed, N. and N. Borenstein, " Multipurpose Internet Mail
Extensions (MIME) - Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC 2046] Freed, N. and N. Borenstein, " Multipurpose Internet Mail
Extensions (MIME) - Part Two: Media Types", RFC 2046,
November 1996.
Dawson & Stenerson Standards Track [Page 144]RFC 2445 iCalendar November 1998
[RFC 2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose
Internet Mail Extensions (MIME) - Part Four: Registration
Procedures", RFC 2048, January 1997.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC 2279] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 2279, January 1998.
[RFC 2425] Howes, T., Smith, M. and F. Dawson, "A MIME Content-Type
for Directory Information", RFC 2425, September 1998.
[RFC 2426] Dawson, F. and T. Howes, "vCard MIME Directory Profile",
RFC 2426, September 1998.
[TZ] Olson, A.D., et al, Time zone code and data,
ftp://elsie.nci.nih.gov/pub/, updated periodically.
[VCAL] Internet Mail Consortium, "vCalendar - The Electronic
Calendaring and Scheduling Exchange Format",
http://www.imc.org/pdi/vcal-10.txt, September 18, 1996.
9 Acknowledgments
A hearty thanks to the IETF Calendaring and Scheduling Working Group
and also the following individuals who have participated in the
drafting, review and discussion of this memo:
Roland Alden, Harald T. Alvestrand, Eric Berman, Denis Bigorgne, John
Binici, Bill Bliss, Philippe Boucher, Steve Carter, Andre
Courtemanche, Dave Crocker, David Curley, Alec Dun, John Evans, Ross
Finlayson, Randell Flint, Ned Freed, Patrik Faltstrom, Chuck
Grandgent, Mark Handley, Steve Hanna, Paul B. Hill, Paul Hoffman,
Ross Hopson, Mark Horton, Daryl Huff, Bruce Kahn, C. Harald Koch,
Ryan Jansen, Don Lavange, Antoine Leca, Theodore Lorek, Steve
Mansour, Skip Montanaro, Keith Moore, Cecil Murray, Chris Newman,
John Noerenberg, Ralph Patterson, Pete Resnick, Keith Rhodes, Robert
Ripberger, John Rose, Doug Royer, Andras Salamar, Ted Schuh, Vinod
Seraphin, Derrick Shadel, Ken Shan, Andrew Shuman, Steve Silverberg,
William P. Spencer, John Sun, Mark Towfiq, Yvonne Tso, Robert Visnov,
James L. Weiner, Mike Weston, William Wyatt.
Dawson & Stenerson Standards Track [Page 145]RFC 2445 iCalendar November 1998
10 Authors' and Chairs' Addresses
The following address information is provided in a MIME-VCARD,
Electronic Business Card, format.
The authors of this memo are:
BEGIN:VCARD
VERSION:3.0
N:Dawson;Frank
FN:Frank Dawson
ORG:Lotus Development Corporation
ADR;TYPE=WORK,POSTAL,PARCEL:;;6544 Battleford Drive;
Raleigh;NC;27613-3502;USA
TEL;TYPE=WORK,MSG:+1-919-676-9515
TEL;TYPE=WORK,FAX:+1-919-676-9564
EMAIL;TYPE=PREF,INTERNET:Frank_Dawson@Lotus.com
EMAIL;TYPE=INTERNET:fdawson@earthlink.net
URL:http://home.earthlink.net/~fdawson
END:VCARD
BEGIN:VCARD
VERSION:3.0
N:Stenerson;Derik
FN:Derik Stenerson
ORG:Microsoft Corporation
ADR;TYPE=WORK,POSTAL,PARCEL:;;One Microsoft Way;
Redmond;WA;98052-6399;USA
TEL;TYPE=WORK,MSG:+1-425-936-5522
TEL;TYPE=WORK,FAX:+1-425-936-7329
EMAIL;TYPE=INTERNET:deriks@Microsoft.com
END:VCARD
The iCalendar object is a result of the work of the Internet
Engineering Task Force Calendaring and Scheduling Working Group. The
chairmen of that working group are:
BEGIN:VCARD
VERSION:3.0
N:Ganguly;Anik
FN:Anik Ganguly
ORG: Open Text Inc.
ADR;TYPE=WORK,POSTAL,PARCEL:;Suite 101;38777 West Six Mile Road;
Livonia;MI;48152;USA
TEL;TYPE=WORK,MSG:+1-734-542-5955
EMAIL;TYPE=INTERNET:ganguly@acm.org
END:VCARD
Dawson & Stenerson Standards Track [Page 146]RFC 2445 iCalendar November 1998
The co-chairman of that working group is:
BEGIN:VCARD
VERSION:3.0
N:Moskowitz;Robert
FN:Robert Moskowitz
EMAIL;TYPE=INTERNET:rgm-ietf@htt-consult.com
END:VCARD
Dawson & Stenerson Standards Track [Page 147]
RFC 2445 iCalendar November 1998
11. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Dawson & Stenerson Standards Track [Page 148]
