Sorry, I was a bit too glib - you can't quite assign an item in iCal to recur on Sept. 1 and Jan 15 every year - but you can assign an item to recur on, say, Sept. 3 and Jan. 3 every year, or the 2nd Tuesday of Sept and Jan every year, etc., which works for what I'm trying to do (have certain reminders that recur once in the Fall semester and once in the Spring).
To do this in iCal, create an item, edit it, choose Repeat - Custom. Set the Frequency to Yearly. Choose whichever months you want the event to recur. Choose which day of the week or day you want it to recur. Done.
So, for example, if I have a meeting that occurs on the first Friday of every month, except the months when school is not in session, I can schedule the event to occur in my calendar on all of those Fridays, except, say, Fridays in the summer.
In addition, iCal will remember exceptions that are made to this recurrence pattern. So if I delete one of those recurring meetings, or move it to a different day or time, this won't mess up the overall pattern of recurrence.
I realize that I'm talking about events, not actions, and so perhaps it's a bit of apples and oranges as far as comparing with OF is concerned, but it is something I use a lot in iCal and wish that OF had more robust rules for setting repeating actions.
Thanks,
AZ