Google calendar RRULE fails when updating but not when initially creating calendar entry

Question

I already have an event entry that I created from my custom calendar with the following RRULE

FREQ=WEEKLY;DTSTART=20201203T090000;INTERVAL=2;BYDAY=TH;EXDATE:20201203T090000

When I update the event without changing the rrule I get an error

Error Message: Google_Service_Exception: { "error": { "errors": [ { "domain": "global", "reason": "invalid", "message": "Invalid recurrence rule." } ], "code": 400, "message": "Invalid recurrence rule." } }

The only thing I can think of is that this rrule has dates in the past. Can anyone confirm that this would be the issue?

Answer 1

FREQ=WEEKLY;DTSTART=20201203T090000;INTERVAL=2;BYDAY=TH;EXDATE:20201203T090000 is not a valid recurrence rule. With all the invalid parts removed the rule would look like this:

FREQ=WEEKLY;INTERVAL=2;BYDAY=TH

DTSTART and EXDATE are separate properties.