February is dragging on just a day longer this year.
But why are there leap years in the first place? The fault, to paraphrase Shakespeare, is in the orbit of the Earth.
Earth takes 365.2422 days to orbit the sun, explains The Old Farmer's Almanac.
And since the Gregorian calendar only has 365 days, an extra day is added to February every four years to make up the difference.
Without that extra day, the calendar would drag by five hours, 48 minutes and 45 seconds every year — a century of this and the calendar would be out of sync with the seasons by 25 days.
But when did it begin? For that, you have to look back to the Roman Empire.
While Julius Caesar ruled, he tasked mathematician and astronomer Sosigenes with creating the Julian calendar, in an effort to replace a series of calendars that existed throughout the empire, according to Encyclopedia Britannica.
Sosigenes suggested a calendar with 365 days and a leap year every four years. It was assumed at the time that a solar year had 365.25 days.
Romans initially marked the leap year every three years due to a mistake in applying Sosigenes' math, but this was rectified under the reign of Augustus, Julius Caesar's successor.
Then in 1582, Pope Gregory XIII corrected the Julian calendar even further. He proclaimed the Gregorian calendar, which more precisely calculated the length of a solar year. It remains in use today.
The math around leap years isn't perfect.
A leap day happens every four years, except for those that can be divided by 100, and cannot be divided by 400, according to Timeanddate.com.
Ergo, the year 2000 had an extra day in February, but the years 1800 and 1900 did not.
In Irish tradition, Feb. 29 marks the only day that a woman can propose to a man, Irish Central said.
The custom reaches back to the fifth century, when Irish nun St. Brigid of Kildare protested to St. Patrick that women had to wait too long for men to ask them to be their wives.
The story goes that St. Patrick allowed women to propose only on the leap day. It's a tradition that later spread to Scotland.
Of course, these days, women can propose any time they'd like. But that hasn't stopped them observing the custom, as this couple did in Edinburgh in 2012.
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