Leap Year Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Apr 06, 2022

Is 2020 a leap year? 🤔 What are the leap year rules? What happens to people born on the 29th of February?

Our leap year calculator will help you answer all these questions and more!

Read the article below and discover how to work out a leap year and find all the interesting leap year dates.

What is a leap year?

Leap years happen every 4 years. We could probably stop there, but we'd love to elaborate:

  • Leap years have 366 days instead of the regular 365 days.

  • The extra day is added in February, creating a new date: the 29th of February, which occurs once in four years. (Our day of the week calculator can tell you the exact day it will fall on.)

Why do we need to add an extra day every four years?

One extra day, added every four years aligns our calendar to the solar calendar. ☀️

The solar (tropical) year describes the time it takes for the sun to be in the exact same position in the sky. This time is usually equal to 365 days, 5 hours, 48 minutes, 45 seconds.

As we can see, these almost 6 extra hours add up over the years, and eventually create a difference of 1 day between our calendar and the solar calendar.

This moment happens every four years (6h * 4 = 24h). And that's why we have to add 1 extra day every four years, to eliminate the possibility of accumulating additional days and enlarging the differences between the calendars. 🌞

How to calculate leap years?

It's time to check if a year is a leap year! It's much easier than you think.

  1. The year must be divisible by 4.

  2. If the year is divisible by 100, it must also be divisible by 400.

Use the following leap year formula:

Year /4 = Number

2020 /4 = 505 - 2020 is a leap year.

After you divide the year by 4, the obtained number should be an integer. That means that its remainder must be equal to 0.

If your year has two zeros at the end (e.g., 1700) you should also check if it can be divided by 400, leaving no remainder.

1700 / 400 = 4¼ - ¼ is a remainder, 1700 is not a leap year.

Now that you know how to determine leap years, it's high time you try our other calendar tools:

Interesting leap years list

Our leap year calculator allows you to find the number of leap years online within a given range - that's how we know that there were precisely 30 leap years since 1900 until 2020. 📅

Let's start with the list:

  • 2020 - Unforgettable. Fires in Australia, floods in other parts of the world, threats of World War III, and the global coronavirus pandemic. Oh, what a year it was! 🦠

  • 2012 - Queen Elizabeth II marks the 60th anniversary of her coronation. US death toll in Afghanistan hits 2000. CERN announces the discovery of a new particle with properties consistent with the so-called God particle (Higgs boson). 👑

  • 2000 - The start of the new millennium - George W. Bush is elected the president of the United States of America for the first time. The first resident crew enters the International Space Station. Concorde, the fastest plane worldwide, crashes after taking-off from Paris. The first presentation of the Human Genome Project. 🧬

  • 1992 - Space shuttle Atlantis takes off from Cape Canaveral carrying equipment to study global warming. Bosnian War begins. The United States conducts its last nuclear test. Microsoft releases Windows 3.1. 🚀

  • 1960 - The year of Africa - 17 African countries declare independence. Viet Cong is created, increasing the tension in Vietnam. Elvis Presley returns home from Germany to the United States, finishing his military duty. Launch of the first navigation system satellite, Transit. New Zealand had its first TV broadcast. 📺

  • 1956 - The year of the Suez Crisis in Egypt. First broadcast of the Eurovision Song Contest. The submarine transatlantic telephone cable opens. Asian flu pandemic originates in China. 🎤

All the leap years since 1900 are as follows:

1904, 1908, 1912, 1916, 1920, 1924, 1928, 1932, 1936, 1940, 1944, 1948, 1952, 1956, 1960, 1964, 1968, 1972, 1976, 1980, 1984, 1988, 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020

Łucja Zaborowska, MD, PhD candidate
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