enabled calendars aren't kept in sync

[forrestguice]

The "calendar window" is only used when initially adding calendars (triggered by clicking a checkbox), however the pref implies that calendars are periodically updated. Entries should be periodically added and removed to keep calendars in sync within this window.

Currently adding or removing entries is a one-time event triggered by the user. They must uncheck/recheck the enabled pref to get calendars in sync. Considering the "window" is specified in years this isn't really much of a problem, but it would be really nice if it was automatic.

[forrestguice]

The app already uses a SyncAdapter to add/remove the custom calendars. The system should periodically call the onPerformSync method, but since the app is using a LOCAL account I don't think it's ever called.

Using a non LOCAL account would allow automatic synchronization, but it also means requesting additional permissions to add/remove accounts.