Question

Why is a leap year necessary?  

Answer 1

A leap year is necessary because the earth takes approximately 365 days and 6 hours to complete one revolution around the sun. To keep the calendar year synchronized with the astronomical year, the extra 6 hours accumulate each year and after four years add up to 24 hours, or one full day. This extra day is added to February every four years, making that year a leap year with 366 days instead of 365, thus correcting the calendar drift caused by ignoring the 6 extra hours each year.