[Roedou]

Thirty days has September, April, June, and November;

All the rest have thirty-one except February alone which has twenty-eight;

Except on every fourth year, when it has 29;

Except on years divisible by 100, when it has 28 again;

Unless the year is also divisible by 1000, when it's back to 29.

[jeroen]

Almost, but the last one should be:

Unless the year is also divisible by 400, when it's back to 29.

[andrewl]

I grew up with this:

  Thirty days has September,
  April, June, and November,
  All the rest have thirty-one except February,
  Which has four and twenty-four,
  'til leap year gives it one day more.

[nimrod_135]

Use your knuckles, with both hands next to each other, from left to right Jan - Dec. Each 'hump' has 31 days.

[philbarr]

Yes, this is the way I remember. My wife quotes the rhyme and I annoy her by pointing out the following issues:

1 - 3 lines of the rhyme at the end are utterly pointless as it's much easier to just remember that leap years are actually a thing.

2 - The fact that it rhymes doesn't help you remember which months you're talking about. It could quite easily be, "30 days hath September; October, November, December" and it would still rhyme but be wrong.

[JoelAnair]

My grandfather used to say "Thirty days has November, all the rest I can't remember."

[gpmcadam]

> 1 - 3 lines of the rhyme at the end are utterly pointless as it's much easier to just remember that leap years are actually a thing.

I was taught:

    Thirty Days has September,
    April, June and November.
    All the rest have Thirty One;
    Except February, it's a different one!

[jimgardener]

or use just the left hand and tap twice on knuckle of forefinger for july and August :)