The history of leap years and the traditions surrounding them

Want to impress a few friends with your knowledge of the leap year or pip them to the post at the pub quiz, well… Did you know?

The leap year’s extra day is necessary because one Earth year (a complete orbit around the Sun) does not take exactly 365 days – it takes 365.2422 days (so there are almost six extra hours which somehow need to be used up each year). Having an extra day on 29th February every four years helps to synchronize the calendar year with the astronomical year.

February was given the extra day because it was the shortest month. That was caused by Julius Caesar being unhappy that the month named after him, July, only had 29 days in the Roman calendar – so he ‘stole’ two days from February and added them to July. At more or less the same time, Julius Caesar’s astronomer, Sosigenes, increased the Roman calendar year from 355 days to 365 days and recommended adding an extra day every four years. This was the basis of the Julian calendar and is how the idea of leap years was born

The Julian calendar was fine-tuned by Pope Gregory and his advisers in 1582. That resulted in years which would normally be a leap year occasionally not having an extra day, in order to correct the remaining small anomaly with astronomical years and so prevent Easter very gradually getting later and later. In the Gregorian Calendar, a year that is divisible by 100, but not by 400, is not a leap year. So while 2000 was a leap year 1700, 1800 and 1900 were not – meaning that three leap years are ‘lost’ every 400 years. Even the Gregorian Calendar will eventually need adjusting again but not for about 10,000 years!

29th February has not always been the extra day in a leap year. For many years 24th February was simply repeated and in Denmark the tradition of women proposing to men still happens on 24th February.

Britain didn’t adopt the leap year until 1752 and Greece, the last European country to make the change, didn’t add 29th February to its calendar until 1923 – two years after the name ‘Filofax’ was created. Interestingly, it was only in 1752 that the first day of the year was deemed to be 1st January – before then, the first day had been in March, which means that 1751 was a short year as it lost a couple of months.

There are many romantic stories about how the tradition of women proposing to men on 29th February began. One of the earliest, from the 5th century, involved St Brigid complaining that women often had to wait for far too long for a man to propose. In reality, the practice didn’t take hold until the 18th century when the leap year day was not recognised by English law – and since the day had no legal status, it was more acceptable for women to break with convention and ask the man they loved to marry them.

The traditions surrounding women proposing in a leap year vary around the world. A refusal to marry by Danish men means they must give the woman 12 pairs of gloves, while Finnish men have to provide enough fabric for a skirt and in Greece, marriage in a leap year is thought to be unlucky, which still results in there being a fifth less weddings in leap years than other years.

Although about 70 percent of British men think there is no problem with a woman popping the question, only about 5 percent of women actually do so. The number of British men who like the idea of women proposing has grown in recent years but, curiously, slightly fewer women are actually taking the plunge.

There is a roughly one in 1,461 chance of being born on a leap day and babies born on 29 February are known as “leapers” or “leaplings”.

When the Gregorian calendar was first adopted, an exclusive and lucrative contract was awarded to Antonio Lilio to print new calendars. Unfortunately for Lilio, the contract had to be rescinded as he was totally unable to keep up with the huge demand. But that’s where we come in…