Tomorrow is a very special day that occurs once every four years: Leap Day! Now, we all know that it’s added to correct for the fact that one cycle of the Earth around the Sun isn’t actually 365 days long, but where did it come from, and how is it observed around the world?
As far back as the Ancient Egyptians, there have been alterations to the calendar to adjust it to match up with the solar or lunar cycle—but it wasn’t until Julius Caesar intervened that the Leap Day, as we know it, came into being.
The Ancient Egyptian calendar was lunar, which meant that months began the morning after a waning crescent moon could no longer be seen. An intercalary (extra) ‘month’ of five days was added every two or three years to make sure that a certain rising of the star Sirius still happened in the right month and season. However, because there was no Leap Day, the calendar slowly cycled out of sync relative to the solar year and an attempt to add a Leap Day in 238 BCE was unsuccessful.
However, Caesar decided to change this in 46 BCE. After having spent some time in Egypt, he understood that they had this ‘wandering’ calendar and called in Greek astronomers and mathematicians to fix it. This was how the Julian calendar of 365 days, with an extra day every four years, was born. (Plus, the name of the month of July!)
This was then updated in 1582, with the introduction of the Gregorian—or Common Era—calendar. Adding one day every four years didn’t account for around eleven minutes’ worth of drift, so Pope Gregory XIII altered when leap days occurred, slightly, to correct the drift of Easter further and further away from the March equinox.
The new rule was that leap days would be added every four years, except for century years that were not divisible by 400 (so, for example, the year 2000 was a leap year, but 1900 was not). This accounted for a lot of the movement of the calendar and kept Easter to within a fixed period. The Common Era calendar was first mainly used by Catholic countries, but now is used by most non-Western countries too for civil purposes.
Still, there are calendars that exist which have to find other ways to account for these differences in the lunar and solar cycles. In the Chinese traditional calendar, they have a 13-month year approximately once every three years, adding their leap month at the end of the year. The Hebrew calendar adds seven leap months (one per year) in every 19-year cycle. The traditional Islamic Hijri calendar is detached from equinoxes and solstices so doesn’t match up to a standard calendar, but the Solar Hijri, used in Iran and Afghanistan, adds an extra day to its final month in a leap year, to try and keep it in line.
What is Leap Day called around the world?
So, why do we call it Leap Day?
Well, in English, it’s because the addition of the 29th February makes all the days after it ‘leap’ over the days they should have been—for example, tomorrow is Saturday 29th February, so 1st March will have ‘leapt’ over where it should have been, Saturday, and be on a Sunday instead.
Makes sense.
In Spanish, it is called día intercalar, which means ‘inserted day.’ French and Italian are similar: jour bissextile and giorno bisestile. Both derive from the Latin for leap year, bissextilis annus—bissextus was called this because in a leap year, the 6th (sext) day before the Calend of March (24th Feb) appeared twice (bi) every leap year.
Germans call this day der Schalttag, where Schalt means switch or switch over. In Japanese, it is 閏日 (urūbi); the first character means ‘leap’ or ‘intercalary’ and the second means day, so, much like the Spanish. Greek is similar too, with ημέρα άλμα (iméra álma). This is ‘day’ plus ‘leap, jump or bound.’
What are some Leap Day traditions?
The most famous one comes from 5th century Ireland. St Bridget asked St Patrick to allow women to propose because single women were complaining that their intended husbands were too shy to ask them. He said he would allow this to happen every leap year—and so St Bridget proposed to him then and there!
St Patrick turned St Bridget down, sadly, but offered her a kiss and a silk gown, therefore kickstarting an Irish tradition: any man who refuses a woman’s Leap Day proposal must give the woman a silk gown.
It seems unlikely this truly happened, but it is a fun story and the tradition has stuck, spreading from Ireland to Scotland, England and Wales.
In Greece, however, it is bad luck to get married on Leap Day—the same is true of Ukraine. For the Greeks, it is because February was the month of the dead for Romans, so adding another day to that month just added to the woe. The tradition was passed on when the Romans conquered Greece and still lives on to some extent to this day.
However, Finland has a similar tradition to the UK and Ireland, so no bad luck there!
A more recent tradition—and it is likely to have as much basis in reality as the story of St Bridget and St Patrick’s meeting—is that of Leap Day William. The American TV series, 30 Rock, came up with the idea of a Leap Day holiday, a little like Halloween or Christmas, with a mythical figure to accompany it.
Leap Day Wiliam is a Santa Claus-like mascot; he’s a gilled creature who lives in the Mariana Trench and trades candy for children’s tears. He wears blue and yellow and if you see anyone not wearing those colours on Leap Day, you are entitled to shout, “Poke your eyes, pull your hair, you forgot what clothes to wear,” and poke and pull.
Maybe not the tradition we want to emulate—but there are people, especially in New York (where the show is set) who have started wearing blue and yellow on Leap Day—so it’s clearly a fun one for them!
Regardless of why we have it, and what the traditions are, the fact is that we have an extra day this year. What are you planning to do with yours?