Leap Years Explained

What is a leap year?

A leap year has 366 days instead of 365, thanks to an extra day added on 29 February. This keeps our calendar aligned with Earth’s orbit around the Sun, which actually takes about 365.24 days.

The leap year rules

A year is a leap year if:

• It is divisible by 4, and
• If it’s divisible by 100, it must also be divisible by 400.

So 2000 was a leap year, but 1900 was not. The next few leap years are 2028, 2032 and 2036.

Why it matters for your age

Over a lifetime you live through many 29 Februarys. If a calculation ignored these extra days, your “total days lived” would be wrong by roughly one day for every four years. That’s why an accurate age calculator counts every leap day.

Born on February 29?

“Leaplings” technically only have a birthday every four years. In common years, most people celebrate on either 28 February or 1 March — and a good calculator will still show your correct age on any date.

Try it yourself

Put this into practice with our free, private calculators.