Leap Year | Leap Year Calculator

A leap year is a year that has 366 days instead of the usual 365. The extra day is added to February, making it 29 days long instead of 28. This adjustment keeps our calendar year synchronized with the Earth’s orbit around the Sun — which actually takes about 365.242 days. Without this correction, the seasons and dates would slowly drift apart over time. When and Why Did Leap Years Start? The concept of leap years began in 46 BC, introduced by Julius Caesar with the Julian Calendar. Later, in 1582, Pope Gregory XIII refined the system and introduced the Gregorian Calendar, which is the one we still use today. The reason for adding a leap day is to keep the calendar aligned with Earth’s revolution. Since Earth takes slightly more than 365 days to complete one orbit, adding an extra day every four years keeps our dates accurate with the seasons. What Would Happen Without Leap Years? If there were no leap years: The calendar and actual seasons would go out of sync. Summers would slowly start appearing in December, and winters in June! Over centuries, the entire time system would become inaccurate. Leap years keep our calendar balanced and reliable. Leap Year Rules A year is a leap year if: It is divisible by 4, and If it is divisible by 100, it must also be divisible by 400. Examples: 2024 - Leap Year (divisible by 4) 2100 - Not a Leap Year (divisible by 100 but not 400) 2000 - Leap Year (divisible by 400) How to Use the Leap Year Calculator Enter any year (for example, 2020, 2023, 2100). Click “Check Leap Year.” Instantly see whether that year is a Leap Year or a Common Year. This Leap Year Calculator is fast, simple, and ideal for students, teachers, developers, and anyone curious about the calendar. Leap Year List (1900–2100) Here’s a quick Leap Year List for reference: 1904, 1908, 1912, 1916, 1920, … 1996, 2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028, … 2096. This list shows how the leap year pattern continues every 4 years — except when a century year (like 2100) isn’t divisible by 400.