Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Check if a year is a leap year, and list leap years in a range.
Leap Year
Leap years 2028-2040: 2028, 2032, 2036, 2040
This tool checks whether a given year is a leap year (366 days, with an extra day added to February) using the exact Gregorian calendar rule, and can also list every leap year within a range -- useful for date-math edge-case testing, historical lookups, or just settling a "was 1900 a leap year" debate (it wasn't).
Enter a year to check. Optionally, enter a range-end year to list every leap year from the entered year through that end year.
A year is a leap year if it's divisible by 4, except century years (divisible by 100), which are leap years only if also divisible by 400. This three-part rule is why 2000 was a leap year but 1900 and 2100 are not -- a common source of off-by-one bugs in naive "divisible by 4" leap year checks.
2028 is divisible by 4 and not a century year, so it is a leap year (366 days). 2100 is divisible by 4 and by 100, but not by 400, so it is not a leap year.
To find a date's position within its year (which depends on whether it's a leap year), see the Day of Year Calculator. For general date arithmetic that correctly handles leap years, use the Date Calculator.
Type a year into the year field to see whether it is a leap year. To list leap years across a span, also fill the end-year field: the tool then lists every leap year from the first year through the end year. Try a hypothetical span such as 1896 to 1912. The tool would list 1896, 1904, and 1908 and skip 1900, since 1900 is divisible by 100 but not by 400. It is a quick way to see the century exception in action, and it saves counting on your fingers when the span is long.
To verify any result yourself, run three checks in order. First, is the year divisible by 400? If yes, it is a leap year (2000, 2400). If not, is it divisible by 100? If yes, it is not a leap year (1900, 2100, 2200, 2300). If not, is it divisible by 4? If yes, it is a leap year (2024, 2028). Otherwise it is a common year. A hypothetical year like 2400 passes the first check immediately, while 2200 fails it, fails the second, and is therefore a common year despite being a multiple of four.
The result applies the Gregorian rule to every year you enter, including years before the calendar was adopted, so it will not match historical civil calendars from earlier eras. It only decides whether a given year has 366 days; it does not calculate day counts between dates. For that, pair it with a date difference tool. Year entries should be whole numbers, and it is worth reading the listed range carefully to make sure the start and end years are in the order you intended.
The extra century-year exception keeps the calendar synced with Earth's actual orbital period (365.2425 days on average with this rule, very close to the true 365.2422-day year) -- a plain "every 4 years" rule would drift by about 3 days every 400 years.
Yes -- it's divisible by 400, so the century-year exception doesn't apply and it follows the normal every-4-years rule.
366 days -- the extra day is added as February 29th.
Yes. The tool checks every year from your entered year through the end year, so a leap year at the end of the range is included.
Divide the year by 400. If it divides evenly, such as 2000 or 2400, it is a leap year. Century years that do not, such as 2100 or 2300, are not.
It adds one day to the year, so day-of-year numbers after February 28 shift by one and the total is 366. That can matter for interest, subscriptions, and date codes.
Reference: U.S. Department of Labor