What is Leap Day?

Have you wondered why some years contain more than 365 days? Let’s leap into why! Leap Day takes place on February 29, an extra day that is added to the Gregorian calendar about every four years. The name may stem from the added day’s effect of causing dates to “leap” forward two days instead of advancing only one day of the week as between normal calendar years. Leap days occur because Earth takes slightly more than a calendar year to revolve around the Sun—about 365.25 days. Without leap days, the start of each season would drift about a quarter of a day later every year, leading to different solstice dates and drifting weather patterns. Leap days were first implemented in the Julian calendar in 46 BCE, which added an extra day every four years. However, this fix actually overcompensated for the issue. The extra fraction of a day in Earth’s orbit is slightly under a quarter of a day, and an added leap day every four years would cause the seasons to start 44 minutes earlier each year. In 1582 the Gregorian calendar solved this issue by eliminating leap days in century years not divisible by 400. As a result, the years 1600 and 2000 contained leap days, but 1700, 1800, and 1900 did not. Different Leap Day customs exist around the world. An Irish tradition called “Ladies’ Privilege” allows women to propose marriage to men on Leap Day in a reversal of traditional gender roles.
In Greece, some view Leap Day as bad luck and avoid marriages on that day—or even in the entire leap year. And in the United States the town of Anthony, Texas, is known as the “Leap Year Capital of the World.” Beginning in 1988, the town has celebrated Leap Day and those born on it with a quadrennial festival.