ICalendar#Events (VEVENT)

file:ICalendarSpecification.png

iCalendar was created in 1998{{cite web | url = https://icalendar.org/ | title = iCalendar.org | publisher = Z Content | access-date = 2018-03-28}} by the Calendaring and Scheduling Working Group of the Internet Engineering Task Force, chaired by Anik Ganguly of Open Text Corporation, and was authored by Frank Dawson of Lotus Development Corporation and Derik Stenerson of Microsoft Corporation. iCalendar data files are plain text files with the extension {{mono|.ics}} or {{mono|.ifb}} (for files containing availability information only). RFC 5545 replaced RFC 2445 in September 2009 and now defines the standard.

iCalendar is heavily based on the earlier vCalendar by the Internet Mail Consortium (IMC) which has the {{mono|.vcs}} file extension.{{cite web | url = http://www.imc.org/pdi/vcal-10.txt | title = vCalendar: The Electronic Calendaring and Scheduling Exchange Format, Version 1.0 | date = 1996-09-18 | publisher = Internet Mail Consortium | archive-url = https://web.archive.org/web/20160321023312/https://www.imc.org/pdi/vcal-10.txt | archive-date = 2016-03-21 | url-status = dead | access-date = 2018-03-28}} After iCalendar was released, the Internet Mail Consortium stated that it "hopes that all vCalendar developers take advantage of these new open standards and make their software compatible with both vCalendar 1.0 and iCalendar."{{cite web | url = https://www.imc.org/pdi/ | title = vCalendar: The Basis for Cross-Platform Scheduling | publisher = Internet Mail Consortium | date = 2006-11-26 | url-status = dead | archive-url = https://web.archive.org/web/20150906130553/http://www.imc.org/pdi/ | archive-date = 2015-09-06 | access-date = 2016-02-28 }}

The memo "Calendar Access Protocol" (RFC 4324) was an initial attempt at a universal system to create real-time calendars, but was eventually abandoned. Instead, iCalendar saw some adoption for such purposes with ad hoc extensions such as GroupDAV and CalDAV emerging as informal standards and seeing some adoption in both client and server software packages.

A first effort to simplify iCalendar standards by the IETF "Calendaring and Scheduling Working Group" (ietf-calsify WG) ended in January 2011 without seeing adoption.{{cite web|url=https://datatracker.ietf.org/wg/calsify/charter/|title=Calendaring and Scheduling Standards Simplification (calsify)|publisher=IETF|access-date=2015-04-05}}{{cite web|url=http://lists.osafoundation.org/pipermail/ietf-calsify/2010-December/002272.html|title=the end of calsify working group– not the end of the mailing list|last=Lear|first=Eliot|date=2010-12-10|work=ietf-calsify mailing list|access-date=2015-04-05|archive-date=2012-12-09|archive-url=https://web.archive.org/web/20121209115511/http://lists.osafoundation.org/pipermail/ietf-calsify/2010-December/002272.html|url-status=dead}} The work was then picked up by the "Calendaring Extensions Working Group" (ietf-calext WG).{{cite web|url=https://datatracker.ietf.org/wg/calext/charter/|title=Calendaring Extensions (calext)|publisher=IETF|access-date=2016-12-01}}

iCalendar data have the MIME content type {{code|text/calendar}}. The filename extension of {{mono|ics}} is to be used for files containing calendaring and scheduling information, {{mono|ifb}} for files with free or busy time information consistent with this MIME content type. The equivalent file type codes in Apple Macintosh operating system environments are {{mono|iCal}} and {{mono|iFBf}}.

By default, iCalendar uses the UTF-8 character set; a different character set can be specified using the "charset" MIME parameter (if the transport method used supports MIME, such as Email or HTTP). Each line is terminated by CR+LF (in hexadecimal: {{mono|0D0A}}). Lines should be limited to 75 octets (not characters) long. Where a data item is too long to fit on a single line it can be continued on following lines by starting the continuation lines with a space character (in hex: 20) or a tab character (in hex: 09). Actual line feeds in data items are encoded as a backslash followed by the letter n or N (the bytes {{mono|5C 6E}} or {{mono|5C 4E}} in UTF-8).

The iCalendar format is designed to transmit calendar-based data, such as events, and intentionally does not describe what to do with that data. Thus, other programming may be needed to negotiate what to do with this data. A companion standard, "iCalendar Transport-Independent Interoperability" (iTIP) (RFC 2446), defines a protocol for exchanging iCalendar objects for collaborative calendaring and scheduling between "Calendar Users" (CUs) facilitated by an "Organizer" initiating the exchange of data. This standard defines methods such as {{code|PUBLISH}}, {{code|REQUEST}}, {{code|REPLY}}, {{code|ADD}}, {{code|CANCEL}}, {{code|REFRESH}}, {{code|COUNTER}} (to negotiate a change in the entry), and {{code|DECLINE-COUNTER}} (to decline the counter-proposal). Another companion standard, "iCalendar Message-based Interoperability Protocol (iMIP)" (RFC 2447), defines a standard method for implementing iTIP on standard Internet email-based transports. The "Guide to Internet Calendaring" (RFC 3283) explains how iCalendar interacts with other calendar computer language (current and future).

The top-level element in iCalendar is the Calendaring and Scheduling Core Object, a collection of calendar and scheduling information. Typically, this information will consist of a single iCalendar object. However, multiple iCalendar objects can be grouped together. The first line must be {{code|BEGIN:VCALENDAR}}, and the last line must be {{code|END:VCALENDAR}}; the contents between these lines is called the "icalbody". The body must include the "{{mono|PRODID}}" and "{{mono|VERSION}}" calendar properties. In addition, it must include at least one calendar component.{{cite IETF|rfc=5545|section=3.6|title=Internet Calendaring and Scheduling Core Object Specification (iCalendar)|sectionname=Section 3.6 Calendar Components|access-date=1 July 2020}}

{{code|VERSION:1.0}} is used to specify that data is in the old vCalendar format. {{mono|VERSION}} is 2.0 for the current iCalendar format as of 2016.

The body of the iCalendar object (the icalbody) contains single-line Calendar Properties that apply to the entire calendar, as well as one or more blocks of multiple lines that each define a Calendar Component such as an event, journal entry, alarm, or one of several other types. Here is a simple example of an iCalendar object with a single calendar containing a single Calendar Component, a "Bastille Day Party" event starting at 5pm on July 14, 1997, and ending at 4am the following morning:From RFC 2445

BEGIN:VCALENDAR

VERSION:2.0

PRODID:-//hacksw/handcal//NONSGML v1.0//EN

BEGIN:VEVENT

UID:uid1@example.com

ORGANIZER;CN=John Doe:MAILTO:john.doe@example.com

DTSTAMP:19970701T100000Z

DTSTART:19970714T170000Z

DTEND:19970715T040000Z

SUMMARY:Bastille Day Party

GEO:48.85299;2.36885

END:VEVENT

END:VCALENDAR

The UID field distributes updates when a scheduled event changes. When the event is first generated a globally unique identifier is created. If a later event is distributed with the same UID, it replaces the original one. An example UID might be Y2007S2C131M5@example.edu, for the 5th meeting of class 131 in semester 2 at a hypothetical college. Email-style UIDs are now considered bad practice, with a UUID recommended instead.{{cite IETF|rfc=7986|section=5.3|title=iCalendar Property Extensions|sectionname=UID Property|access-date=3 October 2022}}

The most common representation of date and time is a tz timestamp such as {{mono|20010911T124640Z}} with the format {{mono|TZ}} for a total fixed length of 16 characters. Z indicates the use of UTC (referring to its Zulu time zone).{{cite IETF|rfc=5545|section=3.3.5|title=Internet Calendaring and Scheduling Core Object Specification (iCalendar)|sectionname=Section 3.3.5 Date-Time}} When used in {{mono|DTSTART}} and {{mono|DTEND}} properties, start times are inclusive while end times are not. This allows an event's end time to be the same as a consecutive event's start without those events overlapping and potentially creating (false) scheduling conflicts.{{cite IETF|rfc=5545|section=3.6.1|title=Internet Calendaring and Scheduling Core Object Specification (iCalendar)|sectionname=Section 3.6.1 Event Components}}

Components include:

• {{mono|VEVENT}} describes an event, which has a scheduled amount of time on a calendar. Normally, when a user accepts the calendar event, this will cause that time to be considered busy, though an event can be set to be {{mono|TRANSPARENT}} to change this interpretation. A {{mono|VEVENT}} may include a {{mono|VALARM}} which allows an alarm. Such events have a {{mono|DTSTART}} which sets a starting time, and a {{mono|DTEND}} which sets an ending time. If the calendar event is recurring, {{mono|DTSTART}} sets up the start of the first event.
• {{mono|VTODO}} explains a to-do item, i.e., an action-item or assignment. Not all calendar applications recognize {{mono|VTODO}} items. In particular, Outlook does not export Tasks as {{mono|VTODO}} items, and ignores {{mono|VTODO}} items in imported calendars.{{cite web|url=https://msdn.microsoft.com/en-us/library/ee624464%28v=exchg.80%29.aspx|website=Microsoft Developer Network|title=[RFC5546] Section 3.4 Methods for VTODO Components|access-date=7 August 2015}}
• {{mono|VJOURNAL}} is a journal entry. They attach descriptive text to a particular calendar date, may be used to record a daily record of activities or accomplishments, or describe progress with a related to-do entry. A {{mono|VJOURNAL}} calendar component does not take up time on a calendar, so it has no effect on free or busy time (just like {{mono|TRANSPARENT}} entries). In practice, few programs support {{mono|VJOURNAL}} entries.
• {{mono|VFREEBUSY}} is a request for free/busy time, is a response to a request, or is a published set of busy time.{{Clarify|date=December 2008}}
• Other component types include {{mono|VAVAILABILITY}}, {{mono|VTIMEZONE}} (time zones) and {{mono|VALARM}} (alarms). Some components can include other components ({{mono|VALARM}} is often included in other components). Some components are often defined to support other components defined after them ({{mono|VTIMEZONE}} is often used this way).{{Clarify|date=December 2008}}

iCalendar is meant to "provide the definition of a common format for openly exchanging calendaring and scheduling information across the Internet". While the features most often used by users are widely supported by iCalendar, some more advanced capabilities have problems. For example, most vendors do not support Journals ({{mono|VJOURNAL}}). {{mono|VTODO}}s have had conversion problems as well.CalConnect, 2004

iCalendar's calendar is also not compatible with some non-Gregorian calendars such as the lunar calendars used in Israel and Saudi Arabia. Although there exist one-to-one mappings between Gregorian and many other calendar scales, the lack of defined {{mono|CALSCALE}} values for those calendars and limitations in various date fields can make native support impossible. For example the Hebrew calendar year may contain either 12 or 13 months, and the Japanese Emperor-based calendar scale contains many eras.

vCalendar and iCalendar support private software extensions, with a "X-" prefix, a number of which are in common usage.

Some of these include:

• X-RECURRENCE-ID: vCalendar 1.0 extension which mimics the iCalendar 2.0 RECURRENCE-ID (Nokia S60 3rd Edition)
• X-EPOCAGENDAENTRYTYPE: defines the client calendar type
• X-FUNAMBOL-AALARMOPTIONS
• X-FUNAMBOL-ALLDAY: All Day event flag
• X-MICROSOFT-CDO-ALLDAYEVENT: Microsoft Outlook all day event flag
• [https://learn.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxcical/cd68eae7-ed65-4dd3-8ea7-ad585c76c736 X-MICROSOFT-CDO-BUSYSTATUS]: Microsoft Outlook status information
• [https://learn.microsoft.com/en-us/openspecs/exchange_server_protocols/ms-oxcical/df1c7988-9908-4ee6-95b0-fcd180b02b44 X-MICROSOFT-CDO-INTENDEDSTATUS]
• X-WR-CALNAME: The display name of the calendar
• X-WR-CALDESC: A description of the calendar
• X-WR-RELCALID: A globally unique identifier for the calendar{{Cite web|title = [MS-OXCICAL]: Property: X-WR-RELCALID|url = https://msdn.microsoft.com/en-us/library/ee179588(v=exchg.80).aspx|website = msdn.microsoft.com|access-date = 2016-02-23}}
• X-WR-TIMEZONE
• X-PUBLISHED-TTL: Recommended update interval for subscription to the calendar
• X-ALT-DESC: Used to include HTML markup in an event's description. Standard DESCRIPTION tag should contain non-HTML version.
• X-FMTTYPE, X-FILEDATE, X-NAME, X-CN, X-STATUS, X-ROLE, X-SENTBY, X-SYMBIAN-DTSTAMP, X-METHOD, X-RECURRENCE-ID, X-EPOCALARM, X-SYMBIAN-LUID, X-EPOCAGENDAENTRYTYPE{{Cite web |date=October 8, 2009 |others=© Nokia Corporation 2011 |title=iCal and vCal Properties |url=http://devlib.symbian.slions.net/s3/GUID-7811C33D-96D3-5001-B4D3-92BF44F39B2C.html |url-status=live |archive-url=https://web.archive.org/web/20210509022426/http://devlib.symbian.slions.net/s3/GUID-7811C33D-96D3-5001-B4D3-92BF44F39B2C.html |archive-date=May 9, 2021 |access-date=2023-11-17 |website=Nokia Symbian^3 Developer's Library v1.1 |language=en}}

xCal is an XML representation of iCalendar data, as defined in {{IETF RFC|6321}}.

jCal is a JSON representation of iCalendar data, as defined in {{IETF RFC|7265}}.

hCalendar is an (x)HTML representation of a subset of iCalendar data using microformats.

hEvent is an HTML representation of a subset of iCalendar data using microformats addressing some accessibility concerns with the hCalendar format.

• {{annotated link|CalDAV}}
• {{annotated link|vCard}}

{{reflist}}

• {{IETF RFC|5545|link=no}} Internet Calendaring and Scheduling Core Object Specification (iCalendar) (replaces {{IETF RFC|2445|link=no}})
• {{IETF RFC|5546|link=no}} iCalendar Transport-Independent Interoperability Protocol (iTIP) (replaces {{IETF RFC|2446|link=no}})
• {{IETF RFC|6047|link=no}} iCalendar Message-Based Interoperability Protocol (iMIP) (replaces {{IETF RFC|2447|link=no}})
• {{IETF RFC|6321|link=no}} xCal: The XML format for iCalendar (iCalendar XML Representation)
• {{IETF RFC|6868|link=no}} update of the data formats for including certain characters, forbidden by the existing specification, in parameter values
• {{IETF RFC|7265|link=no}} jCal: The JSON Format for iCalendar
• {{IETF RFC|7953|link=no}} Calendar Availability
• {{IETF RFC|7986|link=no}} New Properties for iCalendar (additional properties to the iCalendar specification)
• {{IETF RFC|9073|link=no}} Event Publishing Extensions to iCalendar
• {{IETF RFC|9074|link=no}} "VALARM" Extensions for iCalendar
• {{IETF RFC|9253|link=no}} Support for iCalendar Relationships
• {{cite web | url = http://www.calconnect.org/resources/introduction-internet-calendaring | title = An Introduction to Internet Calendaring and Scheduling | date = 2011-10-20 | publisher = CalConnect}}
• {{cite web | url = https://icalendar.org/resources.html | title = iCalendar Resources}}: A list of resources for iCalendar and related standards.

Category:Computer file formats

Category:Calendaring standards

Category:Internet Standards