Speaking as a (reformed) founder of a calendar company (and former editor of some of the calendar related RFCs) this is a fantastic article. But it can get even harder and more complicated - imagine things like how do you ask a user what to do if they put in a start time and a duration vs a start and end time? If DST happens during an instance of the event? Or if they change the start time? Or the duration? Or the end time?
alcinnz