I have a scheduler that displays all US National Holidays. For the most part I have no trouble creating a recurrence rule. For Thanksgiving that occurs every 4th Thursday of November, regardless if the month has 4 weeks or 5 weeks, I could set the recurrence rule like so: FREQ=YEARLY;BYDAY=TH;BYMONTH=11; BYSETPOS=4; INTERVAL=1.
However, the Memorial Day occurs every last Monday of May and it has to take into consideration if the May of a given year has 4 weeks or 5 weeks. How do I establish a recurrence rule for this?