A leap year has 366 days instead of 365. The extra day, February 29 (called Leap Day), is added to keep our Gregorian calendar synchronized with Earth's ~365.2422-day solar year. Without leap years, the calendar would drift by about one day every four years — meaning seasons would shift over time.

How do I know if a year is a leap year?

Apply the three-rule test: (1) Divisible by 4? → potential leap year. (2) Also divisible by 100? → NOT a leap year, unless (3) also divisible by 400 → IS a leap year. In code: isLeap = (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0.

Yes. 2024 ÷ 4 = 506 (exact), and 2024 is not a century year, so it is a leap year. February 29, 2024 was a Thursday.

Yes. 2028 ÷ 4 = 507 (exact) and it is not a century year. February 29, 2028 falls on a Tuesday. The sequence of upcoming leap years: 2028, 2032, 2036, 2040.

Why is 2100 not a leap year?

2100 is divisible by 4 (2100 ÷ 4 = 525), but it is also a century year (divisible by 100). Century years are only leap years if divisible by 400. Since 2100 ÷ 400 = 5.25 (not an integer), 2100 is not a leap year. The same applies to 2200 and 2300. The next century leap year after 2000 will be 2400.

Why was the century-year exception introduced?

A simple 'every 4 years' rule over-corrects the calendar. Earth's orbital period is 365.2422 days, not exactly 365.25. Adding a leap day every 4 years gives 365.25 days/year on average — too much by 0.0078 days. Skipping 3 out of every 4 century years reduces the average to 365.2425, much closer to the true orbital period. The remaining error is less than one day per 3,000 years.

What happens to people born on February 29?

People born on February 29 are called 'leaplings' or 'leap year babies'. They technically have a birthday only every 4 years. For legal purposes (age calculation, contracts, etc.), most jurisdictions count their birthday on either February 28 or March 1 in non-leap years, depending on local law.

What day of the week is February 29 in the next leap years?

February 29, 2028 = Tuesday. February 29, 2032 = Sunday. February 29, 2036 = Friday. February 29, 2040 = Wednesday. The day advances by 1 (or 2 after a century skip) between consecutive leap years.

Are leap years the same in all calendars?

No. The Gregorian calendar (the civil calendar used worldwide) uses the 4/100/400 rule. The Julian calendar (used before 1582) used a simpler 'every 4 years' rule, which is why it is now 13 days behind the Gregorian calendar. The Hebrew calendar adds a leap month in 7 of every 19 years. The Islamic calendar is purely lunar and does not synchronize with the solar year.

What is the probability of being born on a leap day?

There are 97 leap days in every 400-year Gregorian cycle. The total days in 400 years = 365 × 400 + 97 = 146,097 days. So the probability is 1/146,097 × 400 ≈ 1 in 1,461, or about 0.068%. Approximately 5 million people worldwide are born on February 29.

Leap Year Calculator

Check if any year is a leap year. A year is a leap year if divisible by 4, except centuries unless divisible by 400.

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❌2026 is not a leap year.

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Why Do We Have Leap Years?

Earth completes one orbit around the Sun in approximately 365.2422 days — not exactly 365. A calendar with exactly 365 days per year would drift by about 6 hours each year. Over a century, this adds up to a 24-day drift, meaning summer and winter would gradually shift to different months.

The Gregorian calendar (introduced in 1582 by Pope Gregory XIII, replacing the Julian calendar) solves this by adding a 366th day — February 29 — roughly every four years. The precise rule prevents over-correction:

Rule 1:A year divisible by 4 is a leap year (e.g., 2024, 2028).
Rule 2:Exception: century years (divisible by 100) are not leap years (e.g., 1900, 2100 are not leap years).
Rule 3:Exception to the exception: century years divisible by 400 are leap years (e.g., 2000, 2400 are leap years).

Upcoming Leap Years

Leap Year	February 29	Days in Year
2028	Tuesday, February 29	366
2032	Sunday, February 29	366
2036	Friday, February 29	366
2040	Wednesday, February 29	366
2044	Monday, February 29	366
2048	Saturday, February 29	366
2052	Thursday, February 29	366
2056	Tuesday, February 29	366

Century Year Rule

The average Gregorian year length = 365 + 97/400 = 365.2425 days. The true solar year is 365.2422 days. The error is only 0.0003 days per year — less than one day every 3,000 years. Century years 1700, 1800, and 1900 were not leap years. Year 2000 was (divisible by 400). Years 2100, 2200, 2300 will not be. Year 2400 will be.

Leap Year Facts

→About 5 million people worldwide — 'leaplings' — were born on February 29.
→Anthony, Texas and Anthony, New Mexico share the title of Leap Year Capital of the World, hosting a four-day festival every leap year.
→In Irish and Scottish tradition, February 29 is the one day women may propose marriage to men.
→The Chinese lunisolar calendar adds a leap month (not just a day) roughly every 3 years to stay synchronized with the solar year.
→Julius Caesar introduced the original every-4-years leap year in 46 BC (the Julian calendar). The Gregorian reform in 1582 added the century exception.
→2000 was the first year since 1600 that a century year was also a leap year — many people were confused because the rule was not widely known.