Information About Thirty Days
"Thirty days" is better known as "Thirty days hath September", a traditional English mnemonic rhyme. There are many variants of this song and such songs are mostly used in English-speaking nations to keep in mind the lengths of the months in the Julian and Gregorian calendars.
The rhyme is steeped in history. A 15th century medieval version has been found in the manuscript Harley 2341, in the British Library. There is one aspect that is not similar to the modern versions wherein September and November are often reversed.
Alternative Lyrics & Related Songs
Here is a version with the words "leap year"
Thirty days hath September,
April, June and November.
All the rest have thirty-one,
Save February with twenty-eight days clear
And twenty-nine each leap year