As ascertained at Calconnect IV [iCalendar] recurring and repeating meetings still have a bit of mystery and ambiguity associated with them. Resulting in no true interoperability between the current calendaring and scheduling vendors.
How ambiguous is it – take a look at one example from RFC 2445:
First, the "INTERVAL=2" would be applied to "FREQ=YEARLY" to arrive at "every other year". Then, "BYMONTH=1" would be applied to arrive at "every January, every other year". Then, "BYDAY=SU" would be applied to arrive at "every Sunday in January, every other year". Then, "BYHOUR=8,9" would be applied to arrive at "every Sunday in January at 8 AM and 9 AM, every other year". Then, "BYMINUTE=30" would be applied to arrive at "every Sunday in January at 8:30 AM and 9:30 AM, every other year". Then, lacking information from RRULE, the second is derived from DTSTART, to end up in "every Sunday in January at 8:30:00 AM and 9:30:00 AM, every other year". Similarly, if the BYMINUTE, BYHOUR, BYDAY, BYMONTHDAY or BYMONTH rule part were missing, the appropriate minute, hour, day or month would have been retrieved from the "DTSTART" property.
The real issue is that the current recurrences rules provide for all possible cases, when 90% of these do not matter. Does anyone need to be able to create a recurrence rule for an event to repeat every Sunday in January at 8:30:00 AM and 9:30:00 AM, every other year?
While many discussions have occurred on simplifying the rules, no consensus has been reached at this time. By adding extension capabilities to the new draft – we can concentrate on events now and add recurrence and other features in the future.
