Google doesn't return time zone for some calendars

Question

I'm working with Google Calendar API V3 and have some difficulties with handling time zones provided by Google. In the documentation for calendar: Calendars Overview

It's said that time zone for calendar is optional field:

timeZone
string
The time zone of the calendar. (Formatted as an IANA Time Zone Database name, e.g. "Europe/Zurich".) Optional. However, it's also optional in CalendarList (https://developers.google.com/google-apps/calendar/v3/reference/calendarList).

What does Google assume time zone is in case time zone is not specified in both cases?

Answer 1

Timezone is assumed to be the time zone set in the calendar itself.

Request:

GET https://www.googleapis.com/calendar/v3/calendars/primary

Response

{
 "kind": "calendar#calendar",
 "etag": "\"LOjlc76YTigzSZVQwSEE/E756z8zuickcYzaOnj8krCN4-Pk\"",
 "id": "xxxx@gmail.com",
 "summary": "xxx@gmail.com",
 "timeZone": "Europe/Copenhagen"
}

Created new calendar without setting the timezone results in

{
 "kind": "calendar#calendar",
 "etag": "\"W8S50vTLOjlc76YTigzSZVQwSEE/cBQwQ2pDeiLoQ406eiNPZrDEINc\"",
 "id": "ddd5qep4g260mm7fgq8vtgp18@group.calendar.google.com",
 "summary": "testone",
 "timeZone": "UTC"
}