A Leap Year is a year that has 366 days, instead of the usual 365 days. This happens every four years, when the extra day, February 29, is added to the calendar. 

When is the next Leap Year?

The following years are going to be Leap Years:

2024 2028 2032 2036
2040 2044 2048 2052
2056 2060 2064 2068

Why do we have Leap Years?

The extra Leap Day is added to the calendar every four years so that our calendar stays synchronized with the astronomical seasons. 

If our calendar had the same amount of days every year, the calendar would eventually drift away from the events it is supposed to track and coincide with. The extra day corrects this discrepancy between the dating system and the solar system. 

This happens because the Earth's orbit around the Sun takes around 365.25 days. However, it is not possible to represent a quarter of a day in a calendar, so a Common Year in the Gregorian calendar has 365 days. As a result, it does not perfectly align with the solar year. 

This .25 difference is what gradually makes our calendar become out of sync, and over four years that extra day is added to realign the calendar and give Earth that additional time to do a full orbit around the Sun.

If the Leap Year didn't exist, after 100 years of having .25 fewer days, the seasons would be off by 25 days, and the countries in the Northern Hemisphere such as the United States would experience Summer in February. 

How are Leap Years calculated?

When the Gregorian calendar was established, the following rules were designed to calculate Leap Years:

  • For a year to be a Leap Year it needs to be divisible by 4;
  • However, if the year can also be divisible by 100, it cannot be a Leap Year;
  • Unless it is divisible by 400, and then it is a Leap Year.

For example, century years that are divisible by 100, such as 1800 or 1900, can't be Leap Years, unless they are also divisible by 400, as it happens with the years 1600 and 2000, which were Leap Years.

Although this calculation system has worked fairly well, it is still not completely accurate, and scientists are looking for a way to regulate Leap Years better in the future. 

When were Leap Years created?

Leap Years were first introduced in the Julian Calendar, in 45 B.C. . The calendar's only rule for Leap Years was that any year divisible by four was a Leap Year. This created too many Leap Years, and every 128 years the calendar would drift 1 day from the astronomical seasons. 

In 1582, the Gregorian Calendar was introduced, some days were skipped from the Julian Calendar, and a new formula was created to calculate Leap Years. This realigned our calendar with the seasons.

Leap Year Facts and Traditions

  • Since the 5th century, February 29 or Leap Day, has been designated as a day for romance and gender role reversal. Tradition says that on Leap Day women should propose to men. The movie with Amy Adams titled "Leap Day" is about this tradition. 
  • The chances of being born on a Leap Day are of 1 in 1,500. There are currently around 190,000 people in the United States whose birthday is on February 29.
  • A person who is born on a Leap Year is known as a Leapling. Some people believe that those born on a Leap Day are born into good luck.
  • However, in some cultures, it is bad luck to get married on a Leap Year. 
  • The people of the town of Anthony in Texas have declared it to be the Leap Year capital of the world.