which month has four weeks
Approximately. It's four weeks and a little bit more. If it were exactly 4 weeks, all months would start on the same day of the week. February has exactly 4 weeks (in a non-Leap Year), and the other months are all longer than February. There are 52 weeks in a year, and 52 divided by 12 is 4.3. But remember that there is really no such thing as an average month. Some months have 30 days and some have 31, and then there's the short one.