@brianbilston The one I learned at my mother's knee was:
Thirty days hath September,
April, June, and November.
All the rest have thirty-one.
Excepting February,
Which has twenty-eight days clear,
And twenty nine in each leap year.
@brianbilston My aunt saved me the trouble of learning that:
Make a fist. With the forefinger of your other hand, touch each knuckle and each dip between the knuckles and count by month; start over when you get to your pinkyknuckle (July 31). So your forefinger is January (31), the dip between is February (28), the middle finger knuckle is March (31), etc... It works.
#Mnemonic is such a criminally underused word.
A coworrker once asked me if I could devise a mnemonic device to help him remember how many bodies he had buried in 12 different states across the Eastern half of the US.
I was shocked!
He was the first person I met who actually knew what the word "mnemonic" meant and was able to use correctly in a sentence to boot.