Today is Leap Day. Leap Day was Caesar's attempt to reconcile the calendar year with the Earth's actual movement around the Sun … which is actually 365.2421 days. The Chinese, Buddhist and Hebrew calendars are "lunisolar" … or rather, their dates indicate the position of the Moon as well as the Earth in relation to the Sun. There is a gap of eleven (11) days between a year measured by lunar cycle and one measured by the orbit of the Earth. In ancient times, there would be additional months … or "intercalary" or "interstitial" months … added to the calendar to reconcile the disparity. The Romans would add the days to the month of February. But, this was irregular and confusing.
By the reign of Julius Caesar, the cycle was out of sync. Caesar reordered the Roman Calendar … largely still in use today.