DTENDTZIDAmericaNewYork20240101T140000

DTEND TZID in iCalendar refers to the end date-time of an event or task, and the TZID parameter indicates the time zone used for that end time. In iCalendar (RFC 5545), a date-time value can be expressed with a time zone identifier (TZID) or in Coordinated Universal Time (UTC) using a trailing Z. When DTEND is written with TZID, the end moment is interpreted in the specified time zone; when it is written with Z, it is interpreted as UTC; when it has no TZID and no Z, it is a floating time without a fixed zone.

Common syntax examples include:

DTEND;TZID=America/New_York:20231231T235959

or

DTEND:20231231T235959Z

A floating time might appear as

DTEND:20231231T235959

The TZID value typically references an IANA time zone identifier (for example, America/New_York or Europe/London) and may be backed by a VTATEZONE component in the ICS file. The purpose is to remove ambiguity about local end times, especially for events involving participants in multiple time zones or during daylight saving transitions.

Practical considerations include ensuring consistency with DTSTART, and providing a corresponding TZID for the end time or a UTC time to avoid DST-related shifts. Some implementations rely on the system time zone database, so including a VTIDZONE or using UTC times can improve portability across calendar applications.

See also: RFC 5545, IANA time zones, VTIMEZONE, and floating time semantics.