The Date Repeat API is mostly complete and can parse an iCal RRULE and return...

The Date Repeat API is mostly complete and can parse an iCal RRULE and return an array of dates that match the rule. Also added extensive simpletests on a variety of iCal RRULEs to test the logic. Not all iCal elements are included in this version, but the most common ones are. The API is not yet tied back into the Date module, so you can't do anything with it yet.