Someone just asked how to schedule the Monday preceding May 25th. That we can do this is pretty pretty cool, and demonstrating it would have been really impressive if I had remembered that preceding means 'before', but I digress...
This is a similar problem to scheduling election day. The event type to use is "Custom." There are 5 columns in the customer event editor: days of month, months of year, days of week, and year. The criteria in all of these columns has to be true for the event to be true.
For the Monday preceding May 25th, you would select the seven days before 25 in the days of the month column: 18-24. In the months column, you would select May. And finally, you would select Monday in the days of the week column.
As for election day, it is defined as the first Tuesday after the first Monday in November. If it is after the first Monday in November, it cannot be the first day of the month. Therefore, this problem can be rephrased similar to the first problem; it is the first Monday after November 1st. I'll leave the rest to you.
So what about the scenerio that crosses over a month boundary, like say, the Monday after May 29th? Would you select Monday, 30-31 and 1-5, and May-June? No, because Monday May 1-5 would be a valid event. You would have to break that up into two events: First, Monday, May 30-31 and second, Monday, June 1-5.