Leap Year Checker – Is It a Leap Year? Rules and List

Our free leap year checker tells you instantly whether any year is a leap year and shows each step of the rule, so you can see why. It also gives the previous and next leap year and lists every leap year between two years.

The Leap Year Rule

A calendar year has 365 days, but the Earth takes about 365.2422 days to orbit the Sun. Adding one day every four years would overcorrect slightly, so the Gregorian calendar, in use since 1582, skips three leap days every 400 years. The rule has three parts:

• If the year is divisible by 4, it is a leap year...
• ...unless it is divisible by 100, then it is not...
• ...unless it is also divisible by 400, then it is a leap year again.

How to Use the Leap Year Checker

Step 1: Enter the Year You Want to Check

Open the leap year checker and type any year, or click a quick button such as 2024, 2028 or 2100. It starts with the current year. 2028 shows as a leap year with 366 days.

Step 2: See Which Leap Year Rule Applies

The rule list shows each test with a tick or a cross. For 1900, the year passes the divisible by 4 test and is divisible by 100, but it fails the divisible by 400 test, so it is not a leap year.

Step 3: Check the Days and Nearest Leap Years

The cards show the number of days in the year, the days in February and the previous and next leap year. For 2026 that is 365 days, 28 days in February, 2024 before it and 2028 after it.

Step 4: List Every Leap Year in a Range

Enter a start and end year under List leap years. From 2000 to 2100 there are 25 leap years: 2000 and every fourth year up to 2096. 2100 is not included because it fails the 400 rule.

Leap Years in the 21st Century

From 2001 to 2100 the leap years are 2004, 2008, 2012, 2016, 2020, 2024, 2028, 2032 and so on every four years up to 2096. That is 24 leap years in the century, because 2100 is skipped. The next century year that is a leap year is 2400.

Why Leap Years Matter

• Date calculations: spreadsheets, payroll and age calculators need the right number of days in February.
• Birthdays on 29 February: people born on a leap day usually celebrate on 28 February or 1 March in common years.
• Software testing: leap years are a common source of date bugs, so 29 February and years like 1900 and 2000 are good test cases.
• Finance: some interest calculations use 366 days in a leap year.

Leap Year Tips

• Do not assume every year divisible by 4 is a leap year. Century years like 1900 and 2100 are the exception.
• The checker uses the Gregorian calendar rules for every year. Historical dates before 1582 followed the Julian calendar, which had a leap year every four years without exceptions.
• Everything runs in your browser and works offline once the page is loaded.

Frequently Asked Questions