Close your hand into a fist. Count one knuckle, either index or pinky, it doesn't matter. That's January. The dip next to that knuckle, February. Next knuckle, March. And so on. You reach July, count the same knuckle again for August, then continue (or go to the next hand. It works either way and in either direction!).
Knuckles have 31 days, dips have 30 (except February, which we all know just has to be the center of attention)
