Mnemonics for lengths of months

By Bystander

We are now half way through the shortest month of the year. The traditional mnemonic for remembering the lengths of the months has many variants, but one of the commonest is: “Thirty days hath September, / April, June and November; / All the rest have thirty-one, / Save February with twenty-eight days clear / And twenty-nine in each leap year.”

Versions of this rhyme have passed down through the generations since medieval times. The earliest known written version dates from the first half of the 15th century. It appears in a tiny leather-bound codex (110mm × 65mm), written on parchment, and now buried deep in the vaults of the British Library. The book is part of the huge Harley Collection, a hoard of well over 20,000 manuscripts, charters and rolls bought by the British Museum in 1753.

Apart from two 12-line prayers, the little rhyme is the only entry in English among 220 pages of Latin. It appears at the foot of a page listing saints’ days in February, and reads: “Thirti dayes hath novembir / April june and Septembir. / Of xxviij is but oon / And alle the remenaunt xxx and j”. (A lower case j was often used instead of i for a 1 on its own or at the end of a number.)

But poems are not the only form of mnemonic used for remembering the number of days in each month. In France, a popular method uses the knuckles and depressions on the back of the fist. If the four knuckles and the three depressions between them each represent a month, then when you count across them the knuckles represent the first four 31-day months (January, March, May, July) and the depressions represent the shorter months in between (February, April, June). To continue, jump back to the first knuckle (now August), or across to the other fist, and continue for the remaining months (with a depression and a knuckle to spare).

Voilà!