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Enter a year and click calculate to check whether it is a leap year. This uses the official Gregorian calendar leap year rules.
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Leap years occur every 4 years to align the calendar year with the solar year. The Earth takes approximately 365.2425 days to orbit the Sun, so an extra day (Feb 29) is added during leap years.
• A year is a leap year if it is divisible by 4
• BUT NOT a leap year if divisible by 100
• EXCEPT it IS a leap year if divisible by 400
Examples: 2000 ✔, 2020 ✔, 2100 ✘
Without leap years, seasons would slowly shift. Example: After 100 years, summer would begin in December! Leap years keep the Gregorian calendar aligned with Earth’s orbit.
Most commonly asked leap year questions
Yes. It is divisible by 400, so it is a leap year even though it's divisible by 100.
No. It is divisible by 100 but not by 400.
To synchronize the calendar with Earth’s orbit. Otherwise, dates and seasons drift over time.
No. Century years (like 1800, 1900, 2100) must also pass the 400-year rule.
Leap years exist to keep the Gregorian calendar in sync with Earth's orbit around the Sun. Earth takes approximately 365.2425 days to complete one revolution. Without leap years, the calendar would slowly drift, and seasons would no longer align with their usual months. A leap year adds one extra day — February 29 — every four years to correct this offset.
The Gregorian calendar uses three simple rules to determine leap years:
This ensures long-term accuracy of our calendar system. For example,2000 was a leap year, but 1900 was not.
Leap years keep the seasons correctly aligned with the calendar. Without them:
Every leap year prevents a drift of about 6 hours per year, preserving long-term time accuracy.