Which side, which week
Plenty of blocks are swept on the 2nd and 4th Monday on one side and the 2nd and 4th Tuesday on the other. Knowing your street is swept is the easy part. Remembering which morning, for the side you parked on tonight, is where the $83.50 tickets come from.
Sweeping also skips city holidays and picks up on the next scheduled day, which throws off anyone keeping count in their head.