Normally our calendar years are made up of 365 days, but every four years we add a day to make what is known as a ‘leap year’.
February is the lucky month to prosper from this, although it is a little disadvantaged by only having 28 days in the first place.
This year, just like in the years 2012, 1904, 1816, and most other four year interval since the leap years introduction in 1752, February will have 29 days.
The reason? The solar calendar, also known as the Tropical Calendar.
The Tropical Calendar
A year is the time it takes the Earth to fully circumnavigate the sun, which is approximately 365 days, 5 hours, 48 minutes and 47 seconds.
Every four years we add an extra day to the month of February, the month with the fewest days, to keep our calendars on track.
If we didn’t do this the seasons would shift around the calendar, and in 750 years’ time June would find itself in the middle of winter.
The modern calendar
The origins of the modern calendar as we know it dates back to the Roman times.
Julius Caesar introduced the Julian calendar in 46 BC, which consisted of 365 days, with 366 every fourth year.
However, in his calendar February had 30 days and August had 29.
When Caesar Augustus became emperor he changed this so his month had the same amount as Caesar’s, meaning both July and August had 31 days, and reduced February to 28 days to accommodate the amendment.
In 1582 the UK switched to the Gregorian calendar, worked out by Pope Gregory XIII’s astronomers, as they decided Caesar’s calendar wasn’t quite right.
They worked out the Julian Calendar didn’t perfectly reflect the actual time the Earth takes to orbit the sun, or tropical year.
The Gregorian calendar follows three rules to determine which years are leap years: if the year can be divided by four it is a leap year, but if it can be evenly divided by 100 or by 400 then it is not.
Despite this complicated process the calendar is still not perfect, every 3,236 years it will be out by a day.
Comparably, the Julian calendar is currently lagging behind the Gregorian calendar by 13 days.
Leap day birthdays
Statistics expert Courtney Taylor, writing on website About.com, worked out the chances of being born on a leap year as one in 1,461.
The chances of being born on any other day are, as you might guess, four times higher.
Apparently, Mr Taylor says this means 0.07 per cent of the world’s population was born on a leap day, or 4.8 million people.
Those born on a leap year are invited to join the Honour Society for Leap Year Babies, which currently has 11,000 members.
Traditions
There are actually surprisingly few Leap Year traditions, but the custom of women proposing to men is the most famous.
The legend goes that in 5th Century Ireland St Bridget complained to St Patrick about women having to wait too long for men to propose, to which St Patrick allowed women to propose on 29 February.
Although the more observant may note this could still result in a wait of nearly four years, the tradition has nonetheless gained popularity since the 19th Century.
