Loose reccurrence on an Event in Calendar API
If an event has several fix dates, but no real pattern, it is impossible to create a reccurring event, i.e a SeriesMaster and its instances (occurrences). Example: the event starts on Feb 10 and repeats on Feb 20, Mar 02 and Mar 05. Deleting a SeriesMaster should delete all its occurrences too.
Another option: create relations between existing events