The event update mechanism is push based (the application does not consume any resources unless the calendar changes or an event expires and other minor housekeeping tasks such as updating the labels at midnight).

No as that would lead to an inconsistent view on the home screen (if you don't start the scheduler on one day old events won't be removed or the label won't be changed from tomorrow to today). Reacting to entry changes requires a daemon all the time (the platform calendar library uses a file watch for that).