Today is February 29, a rare date that comes once every four years.
For the rest of us the leap year has a special, almost mystical, aura about it.
This exceptional day has been associated with all sorts of weird and wonderful traditions over the years: from the wildly outdated notion that 29 February is the only day when women can propose to men, to the Leap Year Festival held in Anthony, New Mexico, which sees people born on this special day gather to celebrate their rare birthdays together.
As a rule of thumb, leap days come around every four years. But there are exceptions to this rule. For example, at the turn of every century, we miss a leap year. Even though the year is divisible by four, we don’t add a leap day in the years that end in 00.
But there’s an exception to this rule, too. If the year is a multiple of 400, then we do add in an extra leap day again.
At the turn of the millennium, despite being divisible by 100, the year 2000 did, in fact, have a 29 February because it was also divisible by 400.
What are the odds of being born on a Leap Day?
If leap years came around every four years exactly (which they have done for the last 120 years, covering the birthdays of everyone who is alive today) then the probability of being born on a leap day would be one in 1,461.
This means there are probably around 5 million to 5.5 million leaplings in the world right now.
Calculating a Leap Year
This is how the Gregorian calendar calculates leap years:
- If the year is divisible by four, it’s a leap year.
- But if the year can be divided by 100 as well as four, it’s not a leap year.
- However, if the year is divisible by 400, it is a leap year.
