We don’t get to do this very often (only every 1461 days actually), so Happy Leap Day!

Why do we have a leap day anyway?

Although many believe it is because the earth’s rotation is slowing (roughly 1.7 milliseconds each century), it is merely an artifact of our adoption of the Gregorian calendar. The astronomic calendar is roughly 6 hours longer than our 365 day Gregorian calendar year. Hence we add one day to February every four years. However, 6 hours, is also just a rounded number also. In reality, the astronomic year is slightly less than 365.2425 years, meaning 3 leap days, every 400 years are removed! Three out of every 4 century marks, although they fall on a “Leap Year” do not add a day to February, while the 4th does. In recent history this means the years 1700, 1800, and 1900 only had 365 days although they were leap years, while the year 2000, was allowed to be the exception. Next up, the year 2100, only 84 more years away, will be a leap year, but will NOT have a February 29th! Confused yet?