Rather than using this silly poem (which I never was able to learn), one can refer to a handy reference tool that at all (or at least most) of us have: our hands. Start with the pinky knuckle of your left hand. That's January. The trough between that and the next knuckle is February. Count the rest of the months as so. When you get to the last knuckle on your left hand, July, then go over to the index knuckle on your right hand, for August. Continue to the ring finger knuckle of your right hand, for December.

Anytime a month is associated with a knuckle, it has 31 days; when it's in a trough, it doesn't. Everyone knows that February is the funky month, and those months that aren't 31 days long and aren't Februrary are 30 days long.