< MyMonthlCycles Calculators

Leap Year Calculator

Check any year and find out if it's a leap year. Plus get FYIs: why leap years happen, leaplings and February 29th, leap day traditions, and more!

Calculating Leap Year

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What is Leap Year?

Most years have 365 days. Leap years have 366 days: the extra day is February 29th. It takes 365.25 days for Earth to circle the Sun (365.256363 days, a sidereal year, to be more precise!), so the leap year approximately every 4 years is the catch-up day to synchronize the calendar.

What is a Common Year?

A common year is one having 365 days - i.e. a common year is a non-leap year.

When Did Leap Years Start?

Leap Years have been around for over 2,000 years, starting with the Julian Calendar, named after Julius Caesar, which used leap years to align the calendar with earth's solar orbit.

In 1582, the Gregorian Calendar, named after Pope Gregory XIII, and now used by almost every country, resolved inaccuracies in the Julian Calendar which caused the calendar to gain about 1 day every 100 years.

Is Leap Year Every Four Years?

No, a leap year is not every four years. While leap year generally occurs every four years, when the year is evenly divisible by 4 (such as 2012, 2024 and 2032), the exception is that leap year does not occur on century years that are not evenly divisible by 400. The Gregorian Calendar largely fixed imprecision in the Julian Calendar by implementing this exception.

For example, the year 1200 and 2000 were leap years, but years 1700 and 1900 are not.

What is longest time span without a leap year?

Since only century years evenly divisible by 400 are leap years, most centuries are non-leap years. Consequently, an 8 year gap occurs, from the leap year 4 years prior to the century year until four years later.

For instance, this occurred in 1900, which was not a leap year. The last leap year prior to 1900 was in 1896, and the next was in 1904, an eight year span.

Are U.S. Presidential Elections in Leap Years?

U.S. presidential elections are quadrennial, and most occur in leap years, but not all.

The very first U.S. election, called the election of 1789, spanned 2 years, from December 1788 to January 1789, and 1789 was not a leap year. The election of 1800 and 1900 were not in leap years since those century years were not evenly divisible by 400.

Are Summer Olympics in Leap Years?

The Summer Olympics in the modern era, starting in 1896, have all been in leap years except the Olympics in 1900, and in 2021 which was postponed from 2020 due to Covid-19.

What is the most unique birth date?

February 29 is the most unique birth date! That's because it only occurs at most once every four years!

Theoretically*, the probability of being born on any day of the year other than February 29th is 1/365. For Leap Day, the probability is 4 times less: (1/366) / 4.

In actuality, there is not an even distribution of births across dates. According to the US CDC there are more births in Summer and Fall, with the most in August. That seems intuitive: conception occurs in colder months; The Smithsonian provides more details.

* This does not take into account century leap years.

What is the Leap Day Cocktail

In the 1920s, during Prohibition, US born bartender Harry Craddock hopped a boat to the UK, setting up shop at the Savoy Hotel. According to The Savoy Cocktail Book, which he authored, Craddock created and first served the Leap Day Cocktail on February 29, 1928.

The Leap Day Cocktail is martini-like, but with the delectable additions of orange liqueur and lemon. Find the recipe in Craddock's cocktail book, which makes a great leap year gift; Or, on many websites including Serious Eats.

What is February 29th Called?

February 29 is called Leap Day.

What is a Person Born on February 29 Called?

A person born on February 29 is called a leapling.

When do Leaplings Celebrate Non-Leap Year Birthdays?

If Leap Year only comes around every 4 years* what does a person born on Feb 29th do about birthdays the other 3 years? Generally, the person picks either Feb 28 or March 1 to celebrate. But what about turning 18, and being able to vote...? In many countries, including the USA, a person born Feb 29 is considered to be 18 on March 1!

* As noted earlier, most century years are not leap years.

Is Earth the Only Leap Year Planet?

No! According to Nasa, most planets in our solar system have leap years, for the same reason as Earth: to keep the calendar year aligned with the planet's journey around the sun.

What's the Leap Day Tradition of Women Proposing?

In Ireland, dating back to the 5th Century, women were given the green light to propose marriage on February 29th. And, if he refused, she'd be compensated, usually by a dress or gloves, where the latter was to cover the fact that she had no ring. Scotland and a few other countries have had similar traditions.

The 2010 movie Leap Year is a romantic comedy where the main character, played by Amy Adams, plans to propose to her boyfriend in Dublin on Leap Day.

How To Plan a February 29 Baby?

In order for your baby to be born on February 29th, you need to conceive in the year prior to the leap year. Based on LMP, if your cycle started on May 25 of the preceding year, your baby's estimated due date (EDD), using Naegle's Rule, would be February 29, making your baby a leapling! Based on Conception Date, if your baby was conceived on June 8 of the preceding year, baby's EDD, using Naegle's, would be February 29th.

Since only about 5% of babies are born on their estimated due dates, with most being born up to 14 days early or late, there's a greater chance that baby will not be a leapling, though certainly will be born in the leap year! On the other hand, due to the EDD variance of 2 weeks, it also means that the timeframe is wider for conceiving a leapling. For example, a baby conceived on June 10 in the year prior to leap year will be a leapling if born 2 days early!

How to Avoid Baby's Birth Date on February 29th?

If you are trying to conceive in the year prior to a Leap Year, and prefer your baby not be a leapling, calculate avoiding a February 29 due date. For example, if you were trying to conceive (TTC) in 2023, simply enter February 29, 2024 as the due date to avoid. Similarly, if you are TTC in 2027, enter February 29, 2028.