Leap Year Calculator
Check if any year is a leap year, find the next and previous leap years, list all leap years in a date range, and learn the rules of the Gregorian calendar. Perfect for planning, historical research, and satisfying curiosity.
What Is a Leap Year?
A leap year is a calendar year that contains an extra day — February 29 — making it 366 days long instead of the usual 365. Leap years are necessary to keep our calendar aligned with Earth's revolutions around the Sun. Without leap years, our calendar would drift by about 6 hours every year, and after 100 years, it would be off by about 24 days.
The Gregorian calendar, introduced by Pope Gregory XIII in 1582, uses the following rules to determine leap years:
Rule 1: A year is a leap year if it is divisible by 4.
Rule 2: However, if it is divisible by 100, it is not a leap year.
Rule 3: But if it is divisible by 400, it is a leap year.
Examples: 2000 → divisible by 400 → leap year ✅
1900 → divisible by 100 but not 400 → not a leap year ❌
2024 → divisible by 4 but not 100 → leap year ✅
2100 → divisible by 100 but not 400 → not a leap year ❌
This system gives an average year length of 365.2425 days, closely matching the Earth's orbital period of 365.2422 days.
How Does the Leap Year Calculator Work?
The calculator applies the Gregorian calendar rules to determine if a year is a leap year:
- Single Year Mode: Enter any year from 1 to 9999. The calculator shows if it's a leap year, the next and previous leap years, and the number of days in that year.
- Year Range Mode: Enter a start and end year to see all the leap years in that range, with a count of how many were found.
- Next / Previous Mode: Enter a base year to find the nearest leap years before and after it.
The calculator also provides fun facts about leap years and displays the divisibility rules for any year you check.
Why Use This Leap Year Calculator?
- Three Modes: Check a single year, list a range of leap years, or find the next/previous leap years.
- Clear Results: See the leap year status, divisibility rules, and related dates.
- Fun Facts: Learn interesting trivia about leap years and February 29.
- Free & Private: No registration, no data storage.
- Mobile-Friendly: Works on any device.
❓ Leap Year Calculator FAQ
What is a leap year?
A leap year is a year with 366 days instead of 365. The extra day, February 29, is added to keep the calendar year synchronized with Earth's orbit around the Sun.
What are the rules for determining a leap year?
A year is a leap year if: (1) it is divisible by 4, (2) unless it is divisible by 100, in which case it is not, (3) unless it is divisible by 400, in which case it is. This is the Gregorian calendar rule.
Why do we have leap years?
Earth takes approximately 365.2422 days to orbit the Sun. Without leap years, our calendar would drift by about 6 hours each year, and after 100 years, it would be off by about 24 days.
How often does a leap year occur?
Leap years occur approximately every 4 years. However, century years (divisible by 100) are skipped unless they are also divisible by 400. On average, there are 97 leap years every 400 years.
Is 2000 a leap year?
Yes. 2000 is divisible by 4, by 100, and by 400. According to the Gregorian calendar rules, 2000 is a leap year.
Is 1900 a leap year?
No. 1900 is divisible by 4 and by 100, but not by 400. Therefore, it is not a leap year.
Is 2100 a leap year?
No. 2100 is divisible by 100 but not by 400, so it is not a leap year.
What is the next leap year after 2024?
The next leap year after 2024 is 2028. Leap years occur every 4 years unless they fall on a century year not divisible by 400.
How many days are in a leap year?
A leap year has 366 days. February has 29 days instead of the usual 28.
How many days are in a common year?
A common (non-leap) year has 365 days. February has 28 days.
What is the Julian calendar?
The Julian calendar, introduced by Julius Caesar in 45 BCE, used a simpler rule: every year divisible by 4 is a leap year. This resulted in too many leap years, causing the calendar to drift. The Gregorian calendar corrected this.
What is a leap second?
A leap second is an extra second added to Coordinated Universal Time (UTC) to account for the slowing of Earth's rotation. It is not related to leap years, which are about calendar alignment.
What is the difference between a leap year and a leap month?
A leap year adds an extra day (February 29). A leap month (or intercalary month) is an extra month added to some lunisolar calendars, such as the Hebrew calendar or Chinese calendar, to keep them aligned with the seasons.
How do leap years affect birthdays?
People born on February 29 (leaplings) celebrate their birthdays only once every 4 years in common years. Many celebrate on February 28 or March 1 in non-leap years.
What is the Gregorian calendar?
The Gregorian calendar is the most widely used civil calendar today. It was introduced by Pope Gregory XIII in 1582 to reform the Julian calendar. It uses the leap year rules described above.
How many leap years are there in a century?
In a 100-year period, there are typically 24 leap years (every 4 years). However, if the century year is not divisible by 400, there are only 24 leap years. In a 400-year period, there are exactly 97 leap years.
What is the rarest birthday?
February 29 is the rarest birthday, occurring only once every 4 years. About 1 in 1,461 people are born on this day.
How do I check if a year is a leap year in programming?
In most programming languages, you can check if a year is a leap year with the condition: (year % 4 === 0) && (year % 100 !== 0 || year % 400 === 0). This calculator uses the same logic.