Handling Dates and Times

iCalendar provides several value types for dates and times.

Value Types

DATE — YYYYMMDD

DTSTART;VALUE=DATE:20240115

For all-day events, holidays, birthdays.

DATETIME — YYYYMMDDTHHMMSS

DTSTART:20240115T090000

TIME — HHMMSS

Standalone time without a date.

Time Zone Handling

UTC — Append Z:

DTSTART:20240115T090000Z

Floating — No Z or TZID. Same wall-clock time everywhere.

TZID reference — Links to a VTIMEZONE component:

DTSTART;TZID=America/New_York:20240115T090000

Best Practices

• Use UTC for DTSTAMP, CREATED.
• Use TZID for event start/end times.
• Always include referenced VTIMEZONE components.
• Prefer IANA time zone identifiers.
• Avoid floating times for cross-timezone events.