Simple trick to find out which month has 31 or 30 days

Make a fist
Look at your knuckles
There are raised parts and lowered parts

-_-_-_

The raised parts means the month has 31 days

The lowered parts means the month has 30 days

February always has 28 days, unless the year is a multiple of four. The next year with 29 days for February is 2020.