Leap Year A leap year (also known as an interplanetary year or bisexuality year) is a calendar year containing an Extra day (or, in the case of luni solar calendars, a month) added to keep the calendar year synchronized with the astronomical or seasonal year
A Leap Day, February 29, is attached to the calendar during leap years. This special day makes the year 366 days long – not 365 days, like an ordinary year.
When Is the Next Leap Day?
The next leap day is February 29, 2020.
The last Leap Day was on February 29, 2016.
Why Add a Leap Day?
Leap days are required to keep our calendar in association with the Earth’s orbits around the Sun.
It takes the Earth around 365.242189 days – or 365 days, 5 hours, 48 minutes, and 45 seconds – to circle already around the Sun. This is called a tropical year.
Without an additional, or intercalary, day on February 29 nearly every four years, we would lose approximately six hours every year. After only 100 years, a calendar without leap years would be off by about 24 days concerning fixed seasonal days such as the vernal equinox or the winter solstice.
Is There a Perfect Calendar?
Caesar Introduced Leap Year
Roman general Julius Caesar completed the first leap day in his Julian Calendar, which he started in 45 BCE. A leap day was added every four years. At the time, the leap day was February 24, and February was the end month of the year.
Too Many Leap Year
However, adding a leap day every four years was too often and finally, in 1582, Pope Gregory XIII founded the Gregorian Calendar. This calendar, which we still use today, has a more specific formula for calculation of leap years, also known as bissextile years.
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Traditions & Folklore
Leap day as a theory has existed for more than 2000 years, and it is still connected with age-old customs, folklore, and irrationality. One of the most well-known stories is that women propose to their boyfriends, instead of the other way around.
What’s a Leap, Second?
The old Roman Calendar added an extra month every few years to have the correct annual changes, similar to the Chinese leap month.