Thirty days hath (has) 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.

Other version:

Thirty days have November,
April, June, and September.
With 28 there is but one.
All the rest have thirty-one.

or:

Thirty days hath September,
April, June, and November;
All the rest have thirty-one,
Excepting February alone,
And that has twenty-eight days clear
And twenty-nine in each leap year.

or:

Thirty days has September
April, June and November.
All the rest have 31
Except February, it’s a different one
It has 28 days clear,
and 29 each leap year.

or:

Thirty days have November,
April, June, and September.
February has 28 alone,
And all the rest have 31.