date-time-tools

Leap Year Checker

Enter a Gregorian year and check whether it is a leap year, with days in the year, February length, and the rule used.

Tool workspace

The interactive tool requires JavaScript.

Instructions

Enter a Gregorian year from 1 to 9999, such as 2024, 1900, or 2000.
Run the check to see whether the year has 366 days and whether February has 29 days.
Before using the result in a business workflow, confirm that your source rule is Gregorian rather than lunar, fiscal, academic, or regional.

Use this browser-local checker for February 29 validation, annual day counts, spreadsheet checks, schedule systems, and date-field boundaries. It uses the Gregorian calendar rule only and does not call external calendar APIs.

Direct answer

A Gregorian leap year is divisible by 400, or divisible by 4 but not by 100. Leap years have 366 days and February has 29 days; common years have 365 days and February has 28 days.

How to use this tool

  1. Enter a Gregorian year from 1 to 9999, such as 2024, 1900, or 2000.
  2. Run the check to see whether the year has 366 days and whether February has 29 days.
  3. Before using the result in a business workflow, confirm that your source rule is Gregorian rather than lunar, fiscal, academic, or regional.

How leap years are checked

First check whether the year is divisible by 400. If so, it is a leap year. Otherwise, check whether it is divisible by 4 but not by 100. Years that do not meet either condition are common years.

Why 1900 is not a leap year but 2000 is

1900 is divisible by 100 but not by 400, so it is not a Gregorian leap year. 2000 is divisible by 400, so it is a leap year. Century years are the usual edge case.

Scope of this checker

This tool checks Gregorian calendar years only. It does not handle lunar calendars, Julian calendars, religious calendars, fiscal years, school years, holidays, make-up workdays, or company calendars.

Frequently asked questions

Is every year divisible by 4 a leap year?

No. If a year is also divisible by 100, it must be divisible by 400 to be a Gregorian leap year.

How many days are in a leap year?

A Gregorian leap year has 366 days, with 29 days in February. A common year has 365 days and 28 days in February.

Does this work for lunar calendars?

No. Lunar leap months and Gregorian leap years use different rules. This checker only covers Gregorian leap years.

Does the tool upload my year?

No. The check runs locally in your browser without an account, backend service, database, or external API.

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