Leap day: 3 VERIFIED facts you may not know about Feb. 29

February is already the odd month out of the year, with 28 days as opposed to the 30 or 31 days in the other 11 months.

But, during a leap year like 2024, the shortest month of the year gets an extra day. This day, which is always tacked on to the end of February, is commonly referred to as leap day. 

2024 is a leap year, which means this year there will be a Feb. 29. We are VERIFYING three facts about leap day, including whether Julius Caesar started it and if it always happens every four years.  

THE SOURCES

• NASA’s Jet Propulsion Laboratory (JPL)
• Georgia Tech article 
• Washington State University article
• Spanel Planetarium at Western Washington University
• The National Air and Space Museum
• Encyclopedia Britannica
• IrishCentral.com
• Timeanddate.com
• 2007 paper written by Western Kentucky University manuscript assistant Lynn Niedermeier
• Customs House Museum and Cultural Center in Tennessee

QUESTION #1

Did Roman dictator Julius Caesar introduce leap day?

THE ANSWER

Yes, Roman dictator Julius Caesar introduced leap day.

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WHAT WE FOUND

Earth takes about 365.2422 days to make one revolution around the sun, or about 6 hours longer than 365 days, NASA’s Jet Propulsion Laboratory (JPL) at the California Institute for Technology explains.

Those extra hours are the reason why we have a leap day approximately every four years.

Jim Sowell, Ph.D., director of the Georgia Tech Observatory, said in an article published by the university that the creation of leap year can be traced to Roman dictator Julius Caesar. 

Around the same time as Caesar’s rule, Egyptian astronomers could see that the Earth’s orbit was very close to 365.25 days, according to Sowell.

Caesar used that knowledge to standardize the Roman calendar, which had shifted well off the alignment of the solar year, with help from Greek mathematicians and astronomers, according to an article published by Washington State University (WSU). 

He established that every fourth year would be a leap year, adding one more day to February. This is the basis of the Julian calendar, Sowell says. 

“Without leap day, the dates of annual events, such as equinoxes and solstices, would slowly shift to later in the year, changing the dates of each season. After only a century without leap day, summer wouldn’t start until mid-July,” the JPL says on its website. 

QUESTION #2

Do leap years always happen every four years?

THE ANSWER

No, leap years do not always happen every four years. Years that are divisible by 100 but not by 400 are skipped.

WHAT WE FOUND

Leap years typically come every four years, but that is not always the case. 

In the late 1500s, astronomers realized that the solar year isn’t exactly 365.25 days.

“After hundreds of years using the Julian calendar, spring had begun moving into winter. The Catholic Church did not want the celebration of Easter to occur in the winter,” the article published by Georgia Tech says. 

To fix the problem, Pope Gregory XIII established the Gregorian calendar in 1582. It skipped 10 days in October of that year to right the discrepancy and specified new criteria for leap years, according to the article published by WSU.

Under the Gregorian calendar, every year that is divisible by four is a leap year – with an exception. Leap years divisible by 100 are skipped unless they’re also divisible by 400.

“This means that three times out of every four hundred years there are eight years between leap years,” the Spanel Planetarium at Western Washington University says on its website. 

For example, 2000 was a leap year, but the years 1700, 1800 and 1900 were not, according to the National Air and Space Museum. The next time a leap year will be skipped is 2100, the museum says. 

According to the National Air and Space Museum, adding a leap day every four years would actually make the calendar longer by 44 minutes. Over time, this would cause the seasons to drift. 

QUESTION #3

Is leap day also known in some places as “Bachelor’s Day,” when women can propose to men?

THE ANSWER

Yes, there is an Irish tradition known as “Bachelor’s Day” or “Ladies’ Privilege” that allows women to propose to men on leap day. 

WHAT WE FOUND

While anyone can propose to whomever they want, an Irish tradition called “Bachelor’s Day” or “Ladies’ Privilege” allows women to propose marriage to men on leap day “in a reversal or traditional gender roles,” Encyclopedia Britannica explains. 

It is said the tradition began in 5th century Ireland, when it wasn’t socially acceptable for women to propose to men. 

Legend has it that St. Brigid of Kildare complained to St. Patrick that women had to wait far too long for men to propose, IrishCentral.com says. The two are said to have struck a deal to allow women to propose to men on leap day, according to timeanddate.com.

According to the legend, Brigid then dropped straight to her knee and proposed to Patrick, who declined. He is said to have given her a kiss on the cheek and a silk gown to soften the blow. 

The validity of this folktale is dubious since Brigid would have been a child when St. Patrick died, manuscript assistant Lynn Niedermeier wrote for Western Kentucky University. 

Regardless, the Irish tradition eventually spread to Britain, Scotland and even Denmark, with each country adopting their own variation of it, according to the Customs House Museum and Cultural Center in Tennessee.

The Scots are said to have passed a law in 1288 that allowed a woman to propose marriage on leap day and that any man who declined the proposal would have to pay a fine, according to IrishCentral.com. That fine could range from a kiss to a payment for a silk dress or a pair of gloves.

However, it’s worth noting that “historians have searched the books in vain for the much-cited Scottish law,” Niedermeier wrote.

This story is also available in Spanish / Lee este artículo también en español: Día bisiesto: 3 datos verificados que capaz no sepas sobre el 29 de febrero