Why does Leap Day exist?

Why does Leap Day exist?



Leap Day exists to correct for the difference between the calendar year and the astronomical year. The 365 days of the calendar year represent Earth’s movement around the sun every 365 days. But Earth just ate a pizza and is actually moving a bit slower than that: it takes 365 days, 5 hours, 48 minutes, and 46 seconds for Earth to revolve around the sun.

And so, the calendar is adjusted to compensate for that extra time, by adding an extra day to the year about every four years (but not every four years). If we didn’t correct for the difference between the two calendars, the northern hemisphere would eventually end up celebrating New Year’s Eve during summer. In the southern Hemisphere, more cities might see a snowy Christmas. By the year 2736, the US would celebrate the 4th of July in deep winter.

And if you like swirling down an interesting internet search spiral on the mixed-up history of the Julian and Roman calendars, click here.

https://www.geocaching.com/blog/2016/01/when-there-are-366-days-in-a-year/