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Leap Year Checker

Check if a specific year is a Leap Year.

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Is Leap Year?
Days in Year365

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Assumptions

  • The logic follows the Gregorian leap-year rule used by modern civil calendars.
  • Years divisible by 4 are leap years unless they are century years not divisible by 400.
  • This tool checks the year-level rule only and does not account for historical calendar adoption differences by country.

Sensitivity preview

Year -10%: Is Leap Year? No

Year Current: Is Leap Year? No

Year +10%: Is Leap Year? No

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About this Leap Year Check

A leap year contains one extra day, February 29th, making the year 366 days long instead of the usual 365. This is necessary to keep our calendar in sync with the Earth's orbit around the Sun, which takes approximately 365.24 days.

Who this calculator is for

  • Students, teachers, and curious users who want a quick yes-or-no answer for any year.
  • People validating February dates or day counts for schedules, forms, and date logic.
  • Anyone cross-checking calendar calculations that depend on whether a year has 365 or 366 days.

When to use it

  • Confirm whether a year includes February 29 before planning or calculating date spans.
  • Sanity-check day-of-year, age, or add-date results around leap-year boundaries.
  • Use as a quick teaching or reference tool for Gregorian calendar rules.

How to use this calculator

  1. Enter a Year (e.g., 2024, 2000, 1900).
  2. The calculator determines if it has 366 days.

Key assumptions

  • The logic follows the Gregorian leap-year rule used by modern civil calendars.
  • Years divisible by 4 are leap years unless they are century years not divisible by 400.
  • This tool checks the year-level rule only and does not account for historical calendar adoption differences by country.

Accuracy and testing

Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.

View accuracy page

How this calculator works

The logic for the Gregorian calendar is: 1. If the year is divisible by 4, it is a leap year. 2. UNLESS it is divisible by 100, then it is NOT a leap year. 3. UNLESS it is also divisible by 400, then it IS a leap year.

Inputs explained

Year

Any 4-digit year.

Understanding your results

Yes: The year has 366 days and a Feb 29th. No: The year has 365 days.

Example scenarios

2024

Divisible by 4. Not divisible by 100. **Leap Year**.

1900

Divisible by 4. Divisible by 100. Not divisible by 400. **Not a Leap Year**.

2000

Divisible by 4. Divisible by 100. Divisible by 400. **Leap Year**.

Key Features

  • Gregorian Logic
  • Day Count Output
  • Historical/Future Support

Tips & Best Practices

  • The next leap years are 2024, 2028, 2032.
  • Leap seconds are a different concept and are not handled by this rule.

Glossary of Terms

Gregorian Calendar
The internationally accepted civil calendar, introduced by Pope Gregory XIII in 1582.
Solar Year
The time it takes Earth to orbit the Sun (approx 365.2422 days).

Frequently Asked Questions

Why do we need leap years?
Without them, the calendar would drift off by about 6 hours every year. After 100 years, our calendar would be off by 24 days, shifting the seasons.
Was 2000 a leap year?
Yes. Even though it is divisible by 100 (usually not a leap year), it is also divisible by 400, which makes it a leap year.
Is every 4 years a leap year?
Almost. The exception is century years (like 1700, 1800, 1900) that are not divisible by 400.