It used to start "30 days has November"

No, I'm not talking about the calendar . I am talking about the poem about the calendar. The poem, considered by some to be a Nursery Rhyme, and others, like me, to be a necessity, the poem that I repeat every now and then  and sometimes just because  I like the way it sounds,  but mostlybecause I can never remember how many days are in a month.

Thirty days hath September,
April, June and November;
February has twenty-eight alone;
all the rest have thirty-one.
Excepting leap-year - that's the time
when February's days are twenty-nine.

A while back i came upon this information about Welch author Roger Bryan, who believes he has traced the poem back to 1425. explains, “It was in a tiny red leather bound codex written on parchment and is part of the Harley Collection, which comprises more than 7,000 manuscripts and 14,000 charters. These were collected by Robert Harley, later to become the first earl of Oxford, in the early 18th century, which was sold to the British Museum in 1753."
“The beautifully inscribed, four-line entry is at the bottom of a page of saints’ days for the second half of February in a section of religious calendars, and is a rare entry in English – almost everything else is in Latin,” he said.
“It’s one of those rhymes we all seem to know and use regularly. It actually started out as Thirty Days Have November. When or why November and September changed places in the rhyme is not known"

“Groucho Marx was a great fan of the rhyme. He is quoted as saying ‘My favourite poem is the one that starts ‘Thirty days hath September’ because it actually tells you something."

Groucho was right!