Here are two rhymes that have been used for many years to help people remember (or learn) how many days there are in each month:
Thirty days have September,
April, June and November.
All the rest have thirty-one,
excepting February alone,
and that has twenty-eight days clear,
with twenty-nine in each leap year.
Fourth, eleventh, ninth and sixth,
thirty days to each affix;
every other thirty-one,
except the second month alone.