1. What is iCalendar?

iCalendar provides a more precise specification of the calendar components defined in the vCalendar 1.0 specification (VEVENT, VTODO) and defines new calendar components for a journal entry (VJOURNAL), free and busy time information (VFREEBUSY), time zone specification (VTIMEZONE), and alarm definition (VALARM).

The VJOURNAL component allows descriptive notes to be recorded for a particular calendar date. Only a few products implement this component currently.

The grouping of properties in the VFREEBUSY component “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” (from RFC2445).

The timezone specification provided by the VTIMEZONE component provides a more comprehensive replacement for the DAYLIGHT and TZ properties in vCalendar 1.0. It enables date and time information to be communicated in an unambiguous format.

The definition of alarms is provided by the VALARM component. This component provides equivalent functionality to the AALARM, DALARM, MALARM, and PALARM vCalendar 1.0 properties.