Why Did We Just Have A Leap Year?

Did you notice that we had a February 29^th this year? One more day than normal? Which makes 2024 a total of 366 days long rather than the standard 365 days. Every 4 years a Leap Day is added to the end of February creating a Leap Year. And why, you might ask, is that?

The Gregorian calendar we follow shows a 365 day year, but it actually takes the planet a little bit longer than a year to orbit the sun. It takes Earth 365 days, 5 hours, 48 minutes and 46 seconds to orbit the sun, according to NASA. Even though that is rounded down to the 365 days we recognize as a typical year, those nearly 6 extra hours don't just disappear.

Instead, every 4 years a leap day is added to account for the difference. The extra day keeps calendars and seasons from gradually falling out of sync and impacting harvesting, planting and other cycles based on the seasons. Without the addition of Leap Day, in 100 years calendars would be 24 days off, and in 700 years Northern Hemisphere summers would begin in December.

It's because of ancient Roman history that Leap Day falls in February. In the 8th century BC, the calendar was just 10  months long, with the Romans considering winter to be all one period rather than divided into months. Eventually, the Romans established January and February. February, the final month, had the fewest days. Julius Caesar then adjusted the calendar to line it up with the sun, adding Leap Day via decree, but that still didn't fully account for the difference in time. It would be hundreds of years before the problem would be fixed.

In 1582, Pope Gregory XIII adopted the Gregorian calendar which we now use. He specified all years that can be divided by four are leap years, with the exception of century years, which would have to be divisible by 400 to be considered leap years — so while 2000 was a leap year, 2100, 2200, and 2300 will not be. In the 1700s, British law designated Feb. 29 as Leap Day.

Leap years occur every four years unless it falls on a century year that cannot be divided by four. The next leap year will be in 2028. Leap Day that year will be observed on Tuesday, Feb. 29. After that, the next leap year is 2032, when Leap Day falls on Sunday, Feb. 29.