Why sometime february month have 29 days ?

Question

year

Answer 1

A year is made up of 365and1/4 days...every four years each 1/4 day is taken into consideration and accounted for then.

Answer 2

The length of a solar year is 365.25 days, but the calendar is drawn in whole days only.  So every four years, the four 1/4 days are added up to make an extra day.  February was chosen as the month in which the extra day should fall, because that is the month in which it will have the least impact on commerce and legal affairs.