Zulu known issues
Moving Event to another Calendar
Calendars are based on same base Table
In iCal the filter field is simply changed for the event record. No problem.
When an event's calendar is changed in Google Calendar, however, the event is tagged as "deleted" (a 1 is placed in the deleted field) and a new event record is created.
This can be a problem as fields Google doesn't know about are not preserved when the new record is created.
Now the old record is still there, but it is tagged as deleted, and there is no relationship between the old and new record since the new record gets a new Google uuid.
Calendars are based on different Tables
iCal does not work well with this scenario. When an event is moved to another calendar, Zulu rejects the move, and the event is moved back to the original calendar
Google has the same behavior as above.