5 Surprising Facts About Leap Year

While you may know that leap years occur once every four years, you may not be aware of the purpose behind this additional day and even less about its origins This extra day is more than just an oddity on the calendar. Here are 5 things you didn't know about Leap Years...


Leap Day Used to Be Leap Month. The discrepancy between human time and seasonal progression is ancient, with the concept of extra time added to let humans "catch up" to solar time existing for centuries. However, leap time wasn't always as short as a day. The Roman calendar, for example, used to be 355 days long but would add a 22-day month every two years to allow human time to catch up to solar time. Around 46 B.C.E, Julius Caesar decided this was too confusing and created a new calendar, the Julian calendar, that added one leap day every four years. 

Leap Years Are Why We Switched From the Julian Calendar to Gregorian Calendar. Caesar wanted to make leap time less confusing, but his solution didn't help permanently. The extra day every four years without fail led to too many leap days, with human time eventually out of sync with solar time and seasons again. In response, Pope Gregory XIII ordered a new calendar, one that calculated leap days differently. The Gregorian calendar, which is what we use now, was created in 1582, but countries took a couple of centuries to adjust. The Gregorian calendar allows some leap years to be skipped. The -00 years (1800, 1900, etc.) do not have a leap day unless the year is divisible by 400. So 1900 wasn't a leap year, but 2000 was.


Leap Seconds Occur as Needed. If you use any devices that rely on Coordinated Universal Time (UTC), you're relying on atomic clocks, which are highly accurate and rarely need adjustment. While atomic clocks themselves go off by one second maybe every 100 million years, they don't account for the slowing of the Earth's rotation (which is due to tidal effects from the moon and amounts to less than 2 milliseconds of slowing per century). This slowing means that the clocks end up being inaccurate to a small degree and need periodic readjustment. Because the increments of time at play here are so small, the fix is a leap second added every 1 1/2 years. The leap second is scheduled based on predictions and announced by the International Earth Rotation and Reference Systems Service.

February 30 Has Happened Twice. February 30th? Twice in history have countries had to arrange for February 30. In one case, the day occurred as part of the conversion between the Julian and Gregorian calendars; Sweden had to add the day in 1712 because, during its initial attempts to convert in 1700, it made the wrong years leap years. This messed up the country's calendar so badly that everyone had to go back to the Julian calendar temporarily. In 1712, the country made the change to the Gregorian calendar official and added two leap days -- February 29 and 30 -- to catch up. The second time was in the Soviet Union between 1930 and 1931. The Soviet Revolutionary calendar, introduced in 1929, created six 5-day weeks per month, with five to six holidays at the end of the year. That gave February 30 days, but the country continued to observe the Gregorian calendar in everyday life, and the 5-day week was later abandoned.

Famous People Born on Leap Day People born on leap day are often called "leaplings" or "leapers." Most of them don't wait every four years to celebrate their birthdays, but instead blow out the candles on Feb. 28 or March 1. According to History.com, about 4.1 million people around the world have been born on Feb. 29, and the chances of having a leap birthday are one in 1,461. Famous people born on leap day include composer Gioacchino Rossini, motivational speaker Tony Robbins, jazz musician Jimmy Dorsey, actors Dennis Farina and Antonio Sabato Jr., and rapper/actor Ja Rule, to name a few.