The reason leap years have an extra day is to account for the fact that:
A) Earth's rotation period is slowly increasing because of tidal effects.
B) the year is not exactly equal to an integral number of days.
C) the day is not exactly 24 hours because of Earth's periodically varying rotation period.
D) the length of the year varies with a period of 4 years because of precession.

Question

Quizplus · Accepted Answer

A year is actually about 365.2422 days long, which means without the extra day every four years, we would gradually lose about six hours off our calendar each year. This would eventually result in our seasonal and calendar year being completely out of sync. The addition of the extra day in a leap year helps to correct this discrepancy.

The Reason Leap Years Have an Extra Day Is to Account