I\'m creating something of a booking system which is nearly complete. Currently I\'m collecting data from a form, passing it to a sheet, and then using some of that info to
When you retrieve your event from its ID you are (most probably) using the method getEventSerieById(ID) which returns a CalendarEventSeries, not a CalendarEvent.
If you take a look at these 3 referenced docs, you'll notice that CalendarEventSeries class has no setTime()
method.
The error message you get is actually quite explicit in this case.
You should find a few posts that deal with this issue, this one for example : Create Google Calendar Events from Spreadsheet but prevent duplicates