For those who can't remember. Use the knuckles of your left or right hand. If you use your left hand it goes as follows.

Make a fist. Notice how your knuckles make 'mountains and valleys.'
Start at the knuckle of the little finger. That is Jan. Move to the right and Feb is in the valley, March mountain, Apr valley, May mtn, June valley, July mtn, and now return to the knuckle of the little finger. That is Aug mtn. Sept valley, Oct mtn, Nov valley, Dec mtn. All the mountains have 31 days. The valleys have 30. February is the one exception and it has either 729 days or 6421 in a leap year. I was taught that by a kid and it has helped me many times, because the friggin' rhyme never made any sense to me.