Leap Year Rules: Which Years Are Leap Years?
A leap year is divisible by 4, except century years, which must be divisible by 400. See the next leap years and check any year with a free date calculator.
Published · 5 min read
A year is a leap year if it's divisible by 4, except years divisible by 100, which are leap years only if they're also divisible by 400. So 2028 is a leap year, 2100 isn't, and 2000 was. A leap year has 366 days, with the extra day on 29 February. The next leap years are 2028, 2032 and 2036. To check any year, count the days from 1 January to the next 1 January in the free date calculator: 366 means a leap year.
The three rules, in order
Apply them one after another:
- Divisible by 4? If not, it's a common year (365 days). 2026 and 2027 stop here.
- Divisible by 100? If not, it's a leap year. 2028 and 2032 stop here.
- Divisible by 400? If yes, it's a leap year; if not, it's a common year. 2000 was a leap year; 1900 wasn't, and 2100 won't be.
| Year | ÷ 4 | ÷ 100 | ÷ 400 | Leap year? |
|---|---|---|---|---|
| 2026 | No | No | No | No |
| 2028 | Yes | No | No | Yes |
| 1900 | Yes | Yes | No | No |
| 2000 | Yes | Yes | Yes | Yes |
| 2100 | Yes | Yes | No | No |
| 2400 | Yes | Yes | Yes | Yes |
In a spreadsheet, with the year in cell A1, this formula returns TRUE for a leap year:
=OR(MOD(A1,400)=0, AND(MOD(A1,4)=0, MOD(A1,100)<>0))
Why leap years exist
The Earth takes about 365.2422 days to go round the Sun from one spring equinox to the next. A calendar of exactly 365 days would drift by about a quarter of a day each year, and after a century the seasons would be almost a month out.
- Adding a day every 4 years gives an average of 365.25 days. That's the old Julian calendar, and it's slightly too long: it overshoots by about 11 minutes a year.
- Skipping the leap day in three century years out of four (1700, 1800 and 1900 were skipped; 2000 wasn't) brings the average down to 365.2425 days. That's the Gregorian calendar, introduced in 1582 and used for civil purposes almost everywhere today.
The Gregorian average is so close to the real year that it drifts by only about one day in more than 3,000 years.
The next leap years
| Leap year | 29 February falls on |
|---|---|
| 2028 | Tuesday |
| 2032 | Sunday |
| 2036 | Friday |
| 2040 | Wednesday |
| 2044 | Monday |
| 2048 | Saturday |
The last leap year was 2024. Every year divisible by 4 from now until 2096 is a leap year; 2100 is the next one that's skipped.
How to check a year with the date calculator
- Open the free date calculator and choose Days between dates.
- Set the Start date to 1 January of the year, such as 1 January 2028.
- Set the End date to 1 January of the following year, 1 January 2029.
- Read the total: 366 days for a leap year, 365 for a common year.
Or check whether 29 February exists: in Add or subtract time, start from 28 February and add 1 day. In a leap year you get 29 February; otherwise 1 March.
What a leap year changes
- 366 days instead of 365, which is 52 weeks and 2 days instead of 52 weeks and 1 day. That's why your birthday usually moves on by one weekday each year, but by two after a 29 February. See how many weeks are in a year for more on weeks and pay periods.
- Day counts across February are one day longer. From 1 February to 1 March is 29 days in a leap year.
- Adding months and years around 29 February needs care. The calculator caps dates at the end of the month: 29 February 2028 plus 1 year is 28 February 2029, and plus 4 years is 29 February 2032.
- Daily-rate calculations, such as interest or rent worked out per day, sometimes divide by 366 in a leap year and 365 otherwise. Contracts and lenders say which they use.
29 February birthdays
People born on 29 February, sometimes called leaplings, get a real birthday only once every four years. Roughly 1 in 1,461 days is a 29 February, so they're rare but not that rare.
In common years, most celebrate on 28 February (still in February) or 1 March (the day after 28 February). Which date counts officially, for example for coming of age or a licence, depends on the law of the country and sometimes the purpose, so check the local rule if it matters.
The free age calculator treats 28 February as the birthday in common years. Someone born on 29 February 2028 turns 1 on 28 February 2029 by its count, and their half birthday is always 29 August; see the half birthday guide. For exact ages in years, months and days, see calculating age from date of birth.
Leap seconds are different
Leap seconds are occasional one-second adjustments to clock time to keep it in step with the Earth's slightly irregular rotation. They have nothing to do with leap years or the calendar, and international timekeeping bodies have decided to stop adding them by 2035.
Check a year now
Count from 1 January to the next 1 January in the free date calculator to see whether a year has 365 or 366 days. It's free and runs in your browser.
Frequently asked questions
- How do you know if a year is a leap year?
- It must be divisible by 4. If it's also divisible by 100, it must be divisible by 400 too. So 2028 and 2000 are leap years, but 1900 and 2100 aren't.
- When is the next leap year?
- 2028. After that, 2032, 2036 and every fourth year up to 2096.
- Why isn't 2100 a leap year?
- It's divisible by 100 but not by 400. Skipping three leap days every 400 years keeps the calendar in line with the seasons.
- How many days are in a leap year?
- 366. The extra day is 29 February.
- When do people born on 29 February celebrate?
- Most choose 28 February or 1 March in common years. The legal date, where it matters, depends on the country.
Calculators
Try the Date Calculator
Free, no sign-up, works in your browser. Count the days between two dates, in days, weeks, months and weekdays (Monday to Friday), or add and subtract days, weeks, months or years from any date to find the date you need.