50 Fun Facts About Leap Year

How many days does a leap year contain in the Gregorian calendar?

The extra day keeps the calendar year lined up with the seasons, which is why some lunisolar calendars add a whole month instead.

Under the Gregorian rule, a year divisible by 100 is a leap year only if it is also divisible by what?

That is why 2000 was a leap year but 1900 was not and 2100 will not be; the rule removes three leap days every 400 years.

Which of these years was NOT a leap year?

The February 2100 calendar will go straight from the 28th to March 1, just as 1900's did; 1900's missing day famously breaks Microsoft Excel, which still treats it as a leap year for compatibility with Lotus 1-2-3.

Roughly how far does the Julian calendar, with its 365.25-day year, drift from the true seasons?

By 1582 that slow slip had pushed the spring equinox ten days early, which is what prompted the Gregorian reform.

The average Gregorian calendar year works out to how many days?

The mean tropical year is about 365.2422 days, so the Gregorian calendar still gains roughly a day every 3,000 years or so.

Which Roman leader introduced the calendar with a leap day every four years, in 46 BC?

The astronomer Sosigenes of Alexandria is generally credited as the principal designer of the reform that bears Caesar's name.

To realign the seasons before the new calendar began, the year 46 BC was stretched to how many days?

Two extra intercalary months were shoved in between November and December, and the year is still called the 'last year of confusion'.

Which Alexandrian astronomer is considered the main designer of Caesar's calendar reform?

Pliny the Elder is the source for his role; Sosigenes may also have written the almanac Caesar published to help Romans use the new system.

In the original Julian calendar the leap day was created not by adding a 29th day but by doing what?

The doubled day was the 'twice sixth' day before the Kalends of March, which is where the word 'bissextile' for a leap year comes from.

The word 'bissextile', an old term for a leap year, literally means what?

It refers to the doubled sixth day before the Kalends of March; February 29 was not formally recognised in British law until the Calendar Act of 1750.

Which pope's 1582 papal bull instituted the calendar most of the world uses today?

The bull was called Inter gravissimas; the reform itself was based on a proposal by the Calabrian doctor Aloysius Lilius and argued through by the mathematician Christopher Clavius.

When the reform took effect in October 1582, how many days were skipped?

Thursday 4 October was followed directly by Friday 15 October; the weekday cycle was left untouched.

The Calabrian doctor whose proposal formed the basis of the Gregorian reform was named what?

Lilius wanted the ten-day drift removed gradually over forty years; Clavius argued for one clean cut, and Gregory took Clavius's advice.

Britain and its empire, including the American colonies, adopted the Gregorian calendar in which year?

By then the gap had grown to eleven days, and the UK tax year still ends on 5 April, eleven days on from the old Lady Day quarter-day of 25 March.

Britain's Calendar (New Style) Act 1750 removed how many days from September 1752?

The same act moved the start of the legal year in England from 25 March to 1 January, which Scotland had already done in 1600.

Which was the last European country to adopt the Gregorian calendar for civil use, in 1923?

Orthodox countries held out longest; Russia switched in 1918 after the revolution, which is why the 'October Revolution' happened in November by the new calendar.

Which country's calendar actually contained a February 30, in 1712?

Sweden had botched a gradual switch to the Gregorian calendar and added a second leap day to get back onto the Julian system.

The term 'leap year' probably comes from the fact that after the extra day, a fixed date does what?

A date normally moves forward one day of the week each year; after February 29 it jumps two, 'leaping' over a day.

A person born on February 29 is often called a what?

In the UK, Hong Kong and Taiwan a leapling's legal birthday in common years is 1 March; other places use 28 February.

Who supposedly struck the deal with St Patrick allowing women to propose in a leap year?

The legend has Brigid complaining to Saint Patrick that men were too slow to propose; he offered one day every seven years and she talked him down to four.

The Irish leap-day proposal tradition is known by what name?

It is also called Ladies' Privilege, and a man who refused was traditionally expected to buy the woman gloves, a silk gown or, by the mid-20th century, a fur coat.

A dubious story of a 1288 Scottish leap-year law says proposing women had to wear what?

The law is attributed to Queen Margaret of Scotland, who at the time was five years old and living in Norway, which is one reason historians doubt it.

In Finland, what is a man traditionally expected to buy a woman if he turns down her leap-day proposal?

Elsewhere in Europe the price was twelve pairs of gloves, said to be for hiding the embarrassment of a ringless hand.

In which country is marrying during a leap year considered unlucky?

The superstition sits oddly beside the Irish tradition that treats the same year as the best time to propose.

Which pair of towns declared themselves the joint 'Leap Year Capital of the World' in 1988?

The idea came from resident Mary Ann Brown, herself a leapling; the twin towns still hold a leap-year birthday parade and festival every four years.

Frederic in The Pirates of Penzance was born on February 29. How old will he be at his 21st birthday?

The joke depends on 1900 not being a leap year; the opera premiered in New York on 31 December 1879, the only G&S work to open officially in the United States.

Which actress stars with Matthew Goode in Leap Year (2010), about proposing in Ireland on February 29?

Her character Anna is heading for Dublin but a storm lands her in Dingle; the film made $32.7 million on a $19 million budget.

Sadie Hawkins Day, often confused with Leap Day, originated in which comic strip?

Al Capp introduced it on November 15, 1937, as a footrace in which Dogpatch's unmarried women chased the bachelors; college campuses turned it into a dance.

Which composer of The Barber of Seville was born on February 29, 1792?

He lived to 76 but celebrated only 18 actual birthdays; Ann Lee, founder of the Shakers, was another February 29 baby, in 1736.

Which rapper, born February 29, 1976, is one of the best-known modern leaplings?

Motivational speaker Tony Robbins (1960) and Spanish prime minister Pedro Sánchez (1972) share the birthday.

Herman Hollerith's tabulating company later became which corporation?

His punched-card machines processed the 1890 US census; the Computing-Tabulating-Recording Company was renamed International Business Machines in 1924.

Which organisation founded Rare Disease Day on February 29, 2008?

In common years it is held on the last day of February; 2008 was also the 25th anniversary of the US Orphan Drug Act.

What is the first name of 30 Rock's 'Leap Day' mascot who trades candy for children's tears?

He lives in the Mariana Trench and emerges every four years; the episode aired on NBC on February 23, 2012.

The Hebrew calendar inserts Adar I in how many years of every 19-year cycle?

The added month is Adar I, with the regular Adar becoming Adar II; the 19-year pattern is the Metonic cycle.

In the Hebrew calendar, what is the extra 30-day period inserted in a leap year called?

'Rishon' means first: it slots in before the usual Adar, which is then renamed Adar Sheini, or second Adar.

In the Chinese calendar, which numbered month always contains the northern winter solstice?

The intercalary month takes the same number as the month before it, so it might simply be called 'leap second month'.

How many days does the Ethiopian calendar's short thirteenth month have in a leap year?

The little month is called Pagumen and has five days in ordinary years; Ethiopia's leap year comes every four years without the Gregorian century exception.

The Baháʼí calendar has 19 months of 19 days. How many days is that before intercalary days?

The leftover days are inserted so the new year always begins on the March equinox, the same rule the Iranian Solar Hijri calendar uses.

In which year was the leap second introduced?

Twenty-seven have been added since, the most recent on 31 December 2016, so UTC now trails atomic time by 37 seconds.

As of the mid-2020s, how many leap seconds have been added to Coordinated Universal Time in total?

They are irregular because Earth's rotation speeds up and slows down unpredictably; the IERS announces each one only about six months ahead.

In 2022 the General Conference on Weights and Measures voted to stop leap seconds by which year at the latest?

Russia had asked for 2040 because its GLONASS satellite system, unlike GPS, adjusts for leap seconds.

The main reason Earth's rotation is gradually slowing, forcing leap seconds, is what?

The Moon's tides act as a brake, lengthening the day by about 2.3 milliseconds per century on their own.

Which spreadsheet program deliberately keeps a bug treating 1900 as a leap year?

The error was inherited from Lotus 1-2-3, and Microsoft has published an article explaining why it was left in.

Which country's 29 new Signatur trains refused to run on 31 December 2000 over an unrecognised 366th day?

The date bug hit on the last day of a leap year that many programmers had wrongly assumed would not be one, since 2000 is divisible by 100.

Since what year has US Election Day been the first Tuesday after the first Monday in November?

The modern Summer Olympics began in Athens in 1896, another leap year, so the two events have coincided ever since apart from wartime cancellations and the 2020 postponement.

The Gregorian calendar was designed to keep which astronomical event near the 21st of its month?

That date matters because Easter is set from it, and the Church wanted the feast to stop wandering away from spring.

In the UK, what is a leapling's legal birthday in a common year?

Hong Kong has applied the same rule since 1990, and Taiwan's Civil Code implies it too.

In which year will the Revised Julian calendar first disagree with the Gregorian on leap years?

The Revised Julian rule only counts century years leaving a remainder of 200 or 600 when divided by 900.

How many months does the Coptic calendar have?

Twelve months have 30 days and a short thirteenth has five, or six in leap years, following Julian rules.

In the Solar Hijri and Bahá'í calendars, a leap day is added to keep the year starting on what?

Pure lunar calendars such as the Islamic Hijri instead accept drift through the seasons.