Leap Years: The Rule, the Exceptions and the Next One

A year is a leap year if it is divisible by 4, except for century years, which must also be divisible by 400. The next leap year is 2028, and the next 29 February is Tuesday, February 29, 2028, which is 511 days from today. Check any year with our leap year checker.

The rule in three steps

1. If the year is divisible by 4, it is a leap year…
2. …unless it is divisible by 100, in which case it is not…
3. …unless it is also divisible by 400, in which case it is.

So 2024 and 2028 are leap years (divisible by 4). 2100 will not be (divisible by 100 but not 400). 2000 was (divisible by 400).

Why 1900 was not a leap year but 2000 was

1900 divides by 100 but not by 400, so it was a common year with 28 days in February. 2000 divides by 400, so it was a leap year. Many people alive today have only ever seen the simple “every four years” pattern, because 2000 happened to follow it. The next exception is 2100, which will skip its leap day.

Spreadsheets have a famous quirk here: Excel treats 1900 as a leap year for compatibility with very old software, so dates in early 1900 can be off by one day in Excel. Google Sheets does not have this issue.

Why we need leap years at all

The Earth takes about 365.2422 days to go round the Sun and bring the seasons back to the same point. A calendar of exactly 365 days would slip by almost a quarter of a day each year, and the seasons would drift through the months by about one day every four years.

The Julian calendar, introduced in Roman times, added a leap day every four years, giving an average year of 365.25 days. That was slightly too long, and by the 1500s the calendar had drifted about ten days. The Gregorian calendar, introduced in 1582, dropped three leap days every 400 years with the century rule. That makes the average year 365.2425 days (146,097 days in 400 years), close enough that it will take thousands of years to drift by a single day.

Britain and its colonies, including the British-held parts of India at the time, adopted the Gregorian calendar in 1752. The Islamic (Hijri) calendar follows the moon, not the sun, which is why it moves through the seasons; see why Islamic dates move.

The leap day is added at the end of February because February was the last month of the year in the early Roman calendar, so extra days were traditionally inserted there.

The next leap years

Our leap year 2028 page and the what day is February 29 page give more detail.

Born on 29 February

People born on 29 February, often called leaplings, have a real birthday only once every four years. The chance of being born on that day is about 1 in 1,461. In the years between, most celebrate on 28 February or 1 March. Where a legal age matters, such as for a licence or retirement, the rule depends on the country, so check locally rather than assuming. For an exact age, the age calculator handles 29 February correctly.

What a leap year changes

• The year has 366 days, which is 52 weeks and 2 days.
• Dates after February move forward two weekdays from the previous year instead of one.
• Daily rates, such as interest calculated per day or daily wages from an annual salary, may be divided by 366 instead of 365, depending on the contract.
• Any count of days that spans 29 February is one day longer; see how to count the days between two dates.

Frequently asked questions