Date & Time Tools New Tool

Free Online Leap Year Checker With the Rule Shown

Check whether any year is a leap year and see exactly which of the three rules decided it, because the century rule is the one everybody forgets. Also counts the leap years between two years, lists the next ones coming, and works out when a 29 February birthday next falls on the day itself.

Free Forever Nothing Uploaded The Rule Shown Counts A Range

Free Online Leap Year Checker With the Rule Shown

Advertisement Slot (Top Banner) Google AdSense Unit • Responsive Banner

🗓️ Leap Year Checker The rule that decided it · counts a range · 29 February handled

Every date is worked out in your browser. Nothing you type is sent anywhere.

🗓️ Which year?

Year Any year from 1 to 9999. The rule below is applied exactly as written, whatever the year.

Try one of these

1900 and 2100 are the two that catch people out, and 2000 is the exception to the exception.

Is it a leap year?

—

Days in the year—

Days in February—

The rule that decided it—

Previous leap year—

Next leap year—

The three rules, in order, with your own year put through each one.

Rule	Your year	What it says

Recent years, kept in this browser only.

Nothing here yet Press Log to history on the Leap year tab to keep an answer here.

Buy Us A Coffee

Enjoying WizTools123? Help keep our server infrastructure 100% free and open for everyone.

Buy Us A Coffee

Sponsored Content (Below Tool) Google AdSense Placement

How to Check a Leap Year

Three steps, and the second is the useful one.

Type a year Any year at all. There is no need to stay near the present, because the rule is applied exactly as written whatever the year.

Read which rule decided it Not just yes or no. Divisible by four is only the first of three rules, and the century rule is the one that catches people and software out: 1900 was not a leap year and 2000 was.

Or count a whole range Switch to the range option and both years are included. The count comes from the formula rather than by stepping through every year, and the list is shown underneath.

What to Know About Leap Years

Three rules, not one, and the one that catches people out.

Divisible by four is only the first rule. The full rule has three parts: a year divisible by four is a leap year, unless it is also divisible by one hundred, unless it is also divisible by four hundred. So 1900 was not a leap year and 2000 was. A great deal of software has been written that only knows the first part, and it works perfectly for ninety nine years at a time.

The extra day exists because the year is not a whole number of days. The earth takes about 365.2422 days to go round the sun. Adding a day every four years overshoots slightly, which is what the hundred year rule corrects, and that correction overshoots in turn, which is what the four hundred year rule corrects. What is left is an error of about one day in three thousand years.

A 29 February birthday usually comes every four years, but not always. Someone born on 29 February 1896 waited eight years for the next one, because 1900 was skipped. The same will happen around 2100. The page works out the next real 29 February from whichever year you enter, rather than assuming it is four years later.

Counting a range is a formula, not a loop. The number of leap years up to a given year is that year divided by four, minus divided by one hundred, plus divided by four hundred, each rounded down. Counting between two years is one subtraction of those. It is exact and instant whatever the range, and the list is still shown so the count can be checked.

Before 1582 the calendar was different. The Gregorian calendar, with the hundred and four hundred year rules, began in October 1582 and was adopted in different countries at different times. Before that the Julian calendar made every fourth year a leap year with no exceptions. This page applies the Gregorian rule throughout, which is what almost every piece of software does, and says so rather than pretending the question has one answer.

It runs in your browser with nothing uploaded. The arithmetic is in the page, so it works offline once loaded and nothing you type is sent anywhere.

Key Features & Capabilities

What it does, and what it deliberately does not.

The rule that decided it Not just yes or no, but which of the three rules applied and what the division left over.

All three rules shown Divisible by four, by one hundred, by four hundred, each with your own year put through it.

Counts a range Leap years between any two years, by formula rather than by looping, with the list underneath.

29 February handled The next real 29 February from your year, which is not always four years later.

Previous and next The leap year before and after, so the gap is visible when a century breaks the pattern.

Nothing is uploaded It runs in this tab and keeps working offline.

About Leap Years

A leap year has 366 days instead of 365, with the extra day added as 29 February. The reason is that a year is not a whole number of days: the earth takes roughly 365.2422 days to travel once round the sun. Without a correction the calendar would drift against the seasons by about a day every four years, and after a few centuries spring would be arriving in what the calendar called winter.

Adding one day every four years corrects most of that drift, but it overcorrects: four years of 0.2422 days is 0.9688, not a full day. Over a century that small excess adds up to about three quarters of a day, which is why century years are skipped. Skipping all of them removes slightly too much, which is why every fourth century is put back. The result is the rule everybody half remembers: divisible by four, except divisible by one hundred, except divisible by four hundred.

The exception to the exception is the part that gets forgotten, and it is not a trivial detail. The year 2000 was divisible by one hundred and therefore looked like it should be skipped, but it was also divisible by four hundred and so it was a leap year. Software written with only the first rule in mind produced correct results right through the twentieth century and will do so again until 2100, which is exactly what makes the mistake so persistent: it cannot be found by testing with recent dates.

That is why this page shows which rule made the decision rather than just answering yes or no. Seeing that 1900 failed at the hundred rule, and that 2000 was rescued by the four hundred rule, explains the pattern in a way that a bare answer never will. The same reasoning runs through the range counter, which uses the three divisions directly instead of stepping through each year, and still lists the years so the count can be checked by eye.

Frequently Asked Questions

Centuries, 29 February and the years before 1582.

A year is a leap year if it is divisible by four, unless it is also divisible by one hundred, unless it is also divisible by four hundred. So 2024 is, 1900 is not, and 2000 is.

Because it is divisible by one hundred but not by four hundred. Adding a day every four years slightly overcorrects the calendar, and skipping century years takes that excess back out.

2100. It is divisible by one hundred and not by four hundred, so February will have 28 days. A lot of software that works today will be wrong on that date.

Usually 24 or 25, depending on where the century starts and whether its own century year counts. Over four hundred years there are exactly 97.

Normally every four years, but the gap becomes eight years across a skipped century year. Someone born in 1896 waited until 1904.

The Gregorian rule is applied throughout, which is what almost all software does. Before October 1582 the Julian calendar was in use and made every fourth year a leap year with no exceptions, so for historical dates the two rules disagree.

No. The arithmetic runs in your browser, so nothing you type leaves the page and it works offline.