What month has thirty days?

There is a good little rhyme to remember this:

30 Days has September, April, June and November. All the rest have 31 excepting February alone which has 28 and in a leap year 29.

or

Thirty days hath September, April, June and November;

February has twenty eight alone

All the rest have thirty-one

Except in Leap Year, that's the time

When February's Days are twenty-nine

All of them, except February!