You ram or get rammed in the ass once on April 1st, twice on April 2nd, thrice on April 3rd, etc. If you ram on the 1st day you need to ram on all odd days and get rammed on all even days, and if you get rammed on the 1st day you need to get rammed on all odd days and ram on all even days.
Johnny: Loren and I are going to do All Anal April this year! I'm going to ram her on odd days and she is going to ram me with a strap-on on even days! I'm already hard just thinking about it!