A Google EventDateTime ({ dateTime, date, timeZone }). dateTime is RFC3339 with offset.
EventDateTime
{ dateTime, date, timeZone }
dateTime
Optional
All-day date value (YYYY-MM-DD) — treated as UTC midnight when no dateTime is present.
date
YYYY-MM-DD
RFC3339 timed value with offset (e.g. 2026-06-24T15:00:00-07:00 or …Z).
2026-06-24T15:00:00-07:00
…Z
The IANA time zone, when supplied.
A Google
EventDateTime({ dateTime, date, timeZone }).dateTimeis RFC3339 with offset.