Leap Year Calculator
Check if any year is a leap year and explore leap year patterns. Perfect for calendar calculations, historical research, and understanding leap year cycles.
Leap Year Calculator
Check if a year is a leap year and explore leap year patterns
Leap Year Rules:
- • A year is a leap year if it's divisible by 4
- • However, if the year is divisible by 100, it's NOT a leap year
- • Unless the year is also divisible by 400, then it IS a leap year
- • Examples: 2000 (leap), 1900 (not leap), 2004 (leap), 2100 (not leap)
How to Use the Leap Year Calculator
Choose Calculation Type: Select "Single Year" to check one year or "Year Range" to analyze multiple years.
Enter Year(s): Input a single year or specify start and end years for range analysis.
Get Results: View comprehensive leap year information including patterns, timelines, and statistical analysis.
Leap Year Rules & Logic
Basic Rule
A year is a leap year if it is divisible by 4.
Examples: 2004, 2008, 2012, 2016, 2020, 2024
Century Exception
However, if the year is divisible by 100, it is NOT a leap year.
Examples: 1700, 1800, 1900 (not leap years)
Century Leap Year Exception
Unless the year is also divisible by 400, then it IS a leap year.
Examples: 1600, 2000, 2400 (leap years)
Complete Algorithm
Step 1: If year ÷ 4 ≠ 0, then NOT a leap year
Step 2: If year ÷ 100 ≠ 0, then IS a leap year
Step 3: If year ÷ 400 ≠ 0, then NOT a leap year
Step 4: Otherwise, IS a leap year
Historical Context
Gregorian Calendar
Introduced in 1582 by Pope Gregory XIII to correct the Julian calendar's drift. The leap year rules we use today were established then.
Astronomical Year
The Earth takes approximately 365.2422 days to orbit the Sun, not exactly 365.25 days, which is why the 100/400 rule exists.
Calendar Accuracy
The Gregorian calendar is accurate to about 1 day every 3,030 years, making it extremely precise for practical purposes.
Global Adoption
While introduced in 1582, the Gregorian calendar wasn't adopted worldwide until the 20th century in some countries.
Examples & Applications
Recent Leap Years
Green: Past/Current | Blue: Future
Century Years (1600-2400)
Practical Applications
- • Birthday Calculations: People born on February 29th celebrate every 4 years
- • Financial Systems: Interest calculations and loan terms account for leap years
- • Software Development: Date libraries must handle leap year logic correctly
- • Contract Law: Lease agreements and contracts may specify leap year handling
- • Sports Events: Summer Olympics occur every 4 years on leap years
Leap Year Fun Facts
Leap Day Babies
About 4.1 million people worldwide are born on February 29th. They're called "leaplings" or "leapers."
Probability
The chance of being born on leap day is about 1 in 1,461 (approximately 0.068%).
Traditions
In some cultures, February 29th is when women traditionally propose marriage to men.
Next Century Leap Year
The next century year that will be a leap year is 2400, since 2100, 2200, and 2300 are not leap years.