Of course there’s a scientific reason why February 29th appears on the calendar every four years. It has to do with the earth’s rotation around the sun. We’re taught that it takes 365 days for the earth to circle the sun—but it’s actually closer to 365 and a quarter days.
That’s why in 46 B.C. Julius Caesar added an extra day in February every four years. However—that was slightly too often. Because when we jump forward to 1582, the Julian calendar is out of sync by 24 days.
Pope Gregory the 13th then made the final change—creating a rule that feels similar to “i after e, except after c.”
So it goes that a Leap Day will be included every four years—except during a century year that isn’t divisible by 400. For example…there was a Leap Day during the year 2000, but not during 1900.
Which is a scenario we won’t have to worry about until 2400—so we have some time.
