What Is a Leap Year?

A leap year is a year in which an extra day is added to the calendar—February 29. This day is added every four years to ensure that our calendar stays in alignment with Earth's revolutions around the Sun.

Why Do We Need Leap Years?

A complete orbit of Earth around the Sun takes approximately 365.2422 days. If we didn’t account for that extra 0.2422 days each year, our seasons would slowly drift out of sync with our calendar. In about 100 years, we’d be off by roughly 24 days!

Leap Year Rule: Not Every 4 Years

While leap years typically happen every 4 years, there are exceptions. A year is a leap year if it is divisible by 4, but not if it is divisible by 100—unless it is also divisible by 400. For example, the year 2000 was a leap year, but 1900 was not.

Historical Background

The concept of a leap year dates back to the Roman Empire and was refined during the Gregorian calendar reform in 1582, which adjusted the Julian calendar's leap year system to more accurately align with the solar year.

Leap Year Examples

Fun Fact: Leap Day Birthdays

People born on February 29 are often called ‘leaplings’ or ‘leapers.’ They technically get a birthday only once every 4 years, though most celebrate it on February 28 or March 1 during non-leap years.

Why Leap Years Matter

Leap years keep our modern calendar in sync with astronomical events. Without them, we’d eventually be planting spring crops in what our calendars called winter.

Conclusion

Leap years are a simple but powerful adjustment that keeps our calendar aligned with nature. The next time February 29 rolls around, you’ll know exactly why it’s there—and why it matters!

Note: You can use our to quickly find out if a given year is a leap year!