48 Fun Facts About Leap Year

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

A leap year has 366 days: February gets a 29th day so the calendar keeps pace with the roughly 365.24-day solar year; lunisolar calendars such as the Hebrew one 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?

About 3 days every 400 years: the Julian year is 365.25 days but the seasons repeat every 365.2422, a surplus of 0.0078 days a year, so the calendar slips a full day roughly every 128 years.

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

365.2425 days: 400 Gregorian years hold 97 leap days, so 146,097 days divided by 400; the mean tropical year is about 365.2422, leaving a drift of one day in roughly 3,000 years.

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

Julius Caesar, as pontifex maximus, decreed the reform in 46 BC; the Julian calendar, with a 365-day year and one leap day every four years, took effect on 1 January 45 BC.

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

445 days: besides the usual intercalary month after February, two extra months of 33 and 34 days were inserted between November and December, earning 46 BC the nickname '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?

Gregory XIII issued the bull Inter gravissimas on 24 February 1582, ordering the October skip and the new century-year rule; the Jesuit mathematician Christopher Clavius wrote the defence of the scheme.

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?

Aloysius Lilius (Luigi Lilio), a physician from Calabria, proposed removing the accumulated drift gradually over forty years; Christopher Clavius argued for one clean cut, and the pope took Clavius's advice.

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

1752: Britain's Calendar (New Style) Act 1750 brought in the Gregorian calendar that September, and the shift of the old Lady Day quarter-day of 25 March is why the UK tax year begins on 6 April.

Britain's Calendar (New Style) Act 1750 cut how many days from September when it took effect?

Eleven days: Wednesday 2 September was followed by Thursday 14 September; the same act moved the start of England's legal year from 25 March to 1 January, as Scotland had 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?

Leapling is the usual nickname, alongside 'leaper' and 'leap-day baby'; the odds of a 29 February birth are about 1 in 1,461, and a leapling born in 1996 had seen only seven true birthdays by 2024.

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?

Bachelor's Day, also called Ladies' Privilege, is the Irish name for 29 February proposals; folklore says a man who refused owed the woman a silk gown to soften the blow.

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

A red petticoat, worn visibly below the hem as a warning; the 'law' is attributed to Queen Margaret of Scotland, who in 1288 was five years old and living in Norway, 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?

Fabric for a skirt: Finnish custom says a man who declines a 29 February proposal must buy the woman enough cloth to make a skirt; elsewhere in Europe the forfeit was twelve pairs of gloves.

The Leap Year cocktail was created in 1928 at which London hotel?

The Savoy: head barman Harry Craddock mixed the Leap Year cocktail (gin, Grand Marnier, sweet vermouth, lemon) for the hotel's 29 February 1928 celebrations and printed it in The Savoy Cocktail Book in 1930.

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

Anthony, Texas and Anthony, New Mexico, which straddle the state line, took the title in 1988 at the urging of resident Mary Ann Brown, born on 29 February; a leap-year birthday festival followed.

In which year does Frederic of The Pirates of Penzance say he will come of age?

1940: born on 29 February, Frederic has had only five birthdays at 21, so he sings 'In 1940 I of age shall be'; Gilbert overlooked that 1900 was not a leap year, which would push it to 1944.

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

Amy Adams plays Anna, who sets out for Dublin to propose on 29 February but is blown off course to Dingle, where Matthew Goode's innkeeper Declan drives her across Ireland; it grossed $32.7 million.

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

Li'l Abner: Al Capp introduced Sadie Hawkins Day on November 15, 1937 as a footrace in which Dogpatch's unmarried women chased the bachelors; college campuses turned it into a girl-asks-boy dance.

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

Gioachino Rossini, born in Pesaro on 29 February 1792, lived to 76 but saw only 18 actual birthdays because 1800 was not a leap year; Ann Lee, founder of the Shakers, was born on 29 February 1736.

Which rapper was born on 29 February 1976?

Ja Rule (Jeffrey Atkins) was born in Queens, New York on 29 February 1976; motivational speaker Tony Robbins (1960) and Spanish politician Pedro Sánchez (1972) share the birthday.

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

EURORDIS, the European rare-disease patient alliance, launched Rare Disease Day on 29 February 2008, choosing the rarest date; in common years it falls on 28 February, and 2008 marked 25 years 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?

Leap Day William, in 30 Rock's 2012 'Leap Day' episode, lives in the Mariana Trench and emerges every four years to swap candy for children's tears; the episode aired on NBC on February 23, 2012.

The Hebrew calendar adds a leap month in how many years of every 19-year cycle?

Seven: years 3, 6, 8, 11, 14, 17 and 19 of the cycle are leap years with 13 months; the 19-year pattern is the Metonic cycle, in which 235 lunar months nearly equal 19 solar years.

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 11th month: Chinese calendar rules fix the winter solstice (Dongzhi) in month 11, and the month containing the solar term Yushui must be month 1; leap months repeat the number of the month before them.

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

Six days: the little month Pagumen has five days in ordinary years and six in leap years, which come every four years without the Gregorian century exception.

What are the intercalary days of the Baháʼí calendar, inserted before its final month, called?

Ayyám-i-Há, the 'Days of Há', are the four intercalary days (five in leap years) inserted between the 18th month and the fasting month of ʻAláʼ, bringing the 19-month Baháʼí year to 365 or 366 days.

In which year was the leap second introduced?

1972: the first leap second was inserted on 30 June 1972, when UTC was redefined to tick with atomic clocks while staying within 0.9 seconds of Earth-rotation time (UT1).

How many leap seconds had been added to Coordinated Universal Time by the end of 2016?

27: the last one came on 31 December 2016, leaving UTC 37 seconds behind atomic time; they are irregular because Earth's rotation speeds up and slows unpredictably, and the IERS announces each about six months ahead.

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

2035: Resolution 4 of the 27th CGPM in November 2022 agreed to let UTC drift from Earth-rotation time and discontinue leap seconds by 2035 at the latest; Russia had asked for 2040 because GLONASS, unlike GPS, incorporates them.

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?

Microsoft Excel treats 29 February 1900 as a real date so its serial day numbers match Lotus 1-2-3, whose 1983 bug it inherited; changing it would shift every date in old spreadsheets by one day.

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

Norway: on 31 December 2000 the state railway NSB's newest trains would not start because their onboard software did not recognise the 366th day of the year; crews bypassed it by resetting the date to 1 December.

Since when have US presidential elections, nearly always in leap years, used the first-Tuesday-after-first-Monday rule?

1845: Congress fixed the first Tuesday after the first Monday in November for choosing presidential electors, first used in 1848; presidential elections fall in leap years (1800 and 1900 excepted), so they share the year with the Summer Olympics.

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

The spring equinox: the reform restored it to about 21 March, where it had stood at the Council of Nicaea in 325, because the date of Easter is reckoned from it.

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.

Which month opens the Solar Hijri year used in Iran?

Farvardin is the first of the twelve Solar Hijri months; it begins at Nowruz in March and, like the other five spring and summer months, has 31 days, while Esfand has 29 or 30.