A leap year has 366 days instead of 365: February has 29 days. These extra days keep our calendar in sync with Earth's orbit around the Sun (~365.2422 days).

What is the rule for leap years?

A year is a leap year if: (1) divisible by 4, AND (2) if divisible by 100, must also be divisible by 400. So 2000 was a leap year, but 1900 was not.

Why is 2100 not a leap year?

2100 is divisible by 100 but NOT by 400, so it is not a leap year. The next century leap year is 2400.

How often do leap years occur?

Approximately every 4 years. However, century years (1800, 1900) are skipped unless divisible by 400, giving 97 leap years per 400-year cycle.

Leap Year Calculator

Check if any year is a leap year and find upcoming leap years instantly.

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Year

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Documentation

The Leap Year Rule

The Gregorian calendar uses a 400-year cycle. A leap year adds one February 29 to keep the calendar synchronized with Earth's ~365.2422-day orbit around the Sun.

Algorithm

IF (year % 4 == 0)

AND NOT (year % 100 == 0)

OR (year % 400 == 0)

THEN leap year

Disclaimer: Based on the Gregorian calendar system.

Frequently Asked Questions

How to Use

About the Leap Year Calculator

What it calculates

This leap year calculator handles date arithmetic, time zones, calendars, and scheduling utilities. Check if any year is a leap year and find upcoming leap years.

When to use it

Use for planning events, deadlines, workdays, and time-zone aware calculations.

Example

Adjust the inputs above to model your specific scenario with the Leap Year Calculator.

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Leap Year Calculator

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The Leap Year Rule

Algorithm

About the Leap Year Calculator

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