What makes this Leap Year especially unique is that it is also shared with a Presidential election, and the Summer Olympics, and wow February gets an extra day! The Smithsonian has some fun facts about why it’s called a “Leap Year” and why they ‘Donut’ happen every four years. Simple mathematics reveals that the difference between calendar years and sidereal years over four years is not precisely 24 hours, but rather 23.262222 hours. Rounding errors strike again! By adding a leap day every four years, we unintentionally extend the calendar by over 44 minutes. This extra time would eventually cause seasonal drift in our calendar. Hence, not every fourth year is a leap year. The rule states that if a year is divisible by 100 but not by 400, it is not a leap year. For instance, the year 2000 was a leap year, while 1700, 1800, and 1900 were not. The next skipped leap year will be in 2100.
Now that’s a mouthful!