Not to be confused with Apple's Calendar application (previously named iCal).

iCalendar

Filename extension	.ical, .ics, .ifb, .icalendar
Internet media type	text/calendar
Type of format	Calendar data exchange
Standard	RFC 5545 (Updated by: RFC 5546, RFC 6868, RFC 7529, RFC 7986)
Open format?	Yes

iCalendar components and their properties

The Internet Calendaring and Scheduling Core Object Specification (iCalendar) is a media type which allows users to store and exchange calendaring and scheduling information such as events, to-dos, journal entries, and free/busy information.^[1] Files formatted according to the specification usually have an extension of .ics. With supporting software, such as an email reader or calendar application, recipients of an iCalendar data file can respond to the sender easily or counter-propose another meeting date/time. The file format is specified in a proposed internet standard (RFC 5545) for calendar data exchange.^{[nb 1]}

iCalendar is used and supported by many products, including Google Calendar, Apple Calendar (formerly iCal), IBM Notes (formerly Lotus Notes),^[2] Yahoo! Calendar, Evolution (software), eM Client, Lightning extension for Mozilla Thunderbird and SeaMonkey, and partially by Microsoft Outlook and Novell GroupWise.

iCalendar is designed to be independent of the transport protocol. For example, certain events can be sent by traditional e