Leap Day: February 29
When Is the Next Leap Day?
Why Add a Leap Day?
Leap days are needed to keep our calendar in alignment with the Earth's revolutions around the Sun.
It takes the Earth approximately 365.242189 days—or 365 days, 5 hours, 48 minutes, and 45 seconds—to circle once around the Sun. This is called a tropical year.
Without an extra, or intercalary day on February 29 nearly every four years, we would lose almost six hours every year. After only 100 years, a calendar without leap years would be off by approximately 24 days. Seasonal days such as the vernal equinox or the winter solstice would, therefore, shift in relation to the months in the calendar. For example, in 100 years, the Northern Hemisphere's autumnal equinox, which falls in late September, would fall in late August, and in a few centuries, August would become a spring month.
Caesar Introduced Leap Years
Roman general Julius Caesar implemented the first leap day in his Julian Calendar, which he introduced in 45 BCE. A leap day was added every four years. At the time, leap day was February 24, and February was the last month of the year.
Too Many Leap Years
However, adding a leap day every four years was too often and eventually, in 1582, Pope Gregory XIII introduced the Gregorian Calendar. This calendar, which we still use today, has a more precise formula for calculation of leap years, also known as bissextile years.
Traditions & Folklore
Leap day as a concept has existed for more than 2000 years and it is still associated with age-old customs, folklore, and superstition. One of the most well-known traditions is that women propose to their boyfriends, instead of the other way around.