Something special comes around every four years... and we're not just talking about the Olympics. It's the ever-so-elusive 29th February in a year that has 366 days.

In celebration of 2020 being a leap year, here are 5 fun facts about leap years that you (probably) didn't know about.

1. Leap Years are because of the Earth's rotation

It takes the Earth approximately 365.24 days (or 365 days, 5 hours, 48 minutes and 46 seconds [1]) to complete its rotation around the sun. This is one solar year. To make up for that missing 0.24+ days, 29 February is added to the year's calendar every four years.

Bonus: Leap years are in multiples of four, but century years (e.g. 1900, 2000) do not follow this rule [2]. They must be multiples of 400 to be a leap year, so 1900 and 2100 are not leap years. In summary, leap years are divisible by four, but centuries are an exception whereby only the years that are divisible by 400 are leap years.

Don't worry, we've made it simpler for you to find out if a year is Leap or not. 8-) Check out our Leap Year Generator below! Simply input the range of the years you want to check, and voila! the years which qualify as Leap years will appear. #themagicofcode #leapyeargeneratorftw

2. Thank Julius Caesar for Leap Day

Before Julius Caesar took over the Roman Empire, it was a 355-day-a-year system, where there would be an extra 22-day month every two years [2]. He had his astronomer, Sosigenes, modify the system into having a leap day every four years.

In 1582, Pope Gregory XIII and his astronomers improved it to come up with the Gregorian calendar. It was then decided that there would be no leap year every 400 years, which is how leap day as we know it came to fruition [3].

3. Leap Days/Months/Years are different in other calendars

While the Gregorian calendar (the one that is mainly used) stipulates that 29 February is the Leap Day, this isn't the case in other calendars.

• The official Indian calendar arranges its months differently from the Gregorian calendar. The first half of the year have 31 days, while months in the second half of the year, so the leap day is planned close to 29 February [3, 4].

• The Chinese calendar has 12 months with 353 to 355 days in a year. A leap year happens every three years where a month is added and the year has 383 to 385 days instead. The leap month even has the same name as the previous month! [5, 6]

Leap days and years happen for other planets too! Its own orbit around the sun to make up a year are not exact as well, so these 'leaps' happen to 'make up for it'. On Mars, for example, a year is made up of 668.599 Martian days. Every three years, a day is subtracted – so the leap days are then divisible by 2 or 5 [7, 8].

Bonus: The odds of being born on 29th February, a leap day, is one in 1,461 [2]. What's the math behind this? It's simply the probability of being born once every four years, but since the fourth year has 366 days, the sum is: 365 + 365 + 365 + 366 = 1,461

4. The Leap Year Capital of the World is Anthony

In 1988, neighbours Mary Ann Brown and Birdie Lewis and leaplings (people born on 29 February) got the idea to create a festival to celebrate Leap Day. Officials gave them the go-ahead, so the little town has been celebrating with a four-day Leap Year Festival every four years complete with music, food and fun! [9, 10]

This year is no exception. It's held in Anthony, on the border of Texas and New Mexico, in the United States of America [9], and has been declared by the governors as the Leap Year Capital of the World.

5. Women used to propose on this day

Back then, it was a tradition for men to propose, but on leap days, women could pop the question instead. There have been various origin stories of how this came about.

Legend goes that St Bridget complained to St Patrick that women had to wait too long for suitors to propose in the 5th Century, so he granted 29th February as the day for women to propose. [2, 3] Another common story is that adding 29th February every four years was deemed as 'ridiculous' and was not recognised by the English law as a day. As it was not a 'legal day', traditions could be broken on this day and a British play joked that it was a day where women should act like men. This inspired women to propose to men on Leap Day – eventually evolving into Bachelor's Day or Sadie Hawkins Day – an event still celebrated in the United Kingdom today. [2, 11]

Another legend is that Queen Margaret of Scotland decreed that men would get fined for turning down marriage proposals by women in the leap year [2]. In Denmark, 12 pairs of gloves must be given to the woman if a Danish man refuses the marriage proposal. As for Finland, fabric for a skirt is given instead. In Greece, getting married in a leap year is considered unlucky. [2, 9]

Of course, it's more common for women to propose marriage now! Did you hear about the lady who proposed to her boyfriend at the football match between Manchester United and Inter Milan at Singapore's National Stadium? You can read about it here.

Bonus: a hotel in Iceland is offering a free stay for couples if women propose on Leap Day [12].

Special fun fact (18+): The Leap Year cocktail  

Let's toast to it! In 1928, pioneering bartender Harry Craddock at London's renowned Savoy Hotel invented the Leap Day Cocktail. He published it in his 1930 The Savoy Cocktail Book. [9, 11]

(Written by Cheryl Tang)