Calendar Trivia
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100 free Calendar trivia questions with answers — science & nature quiz, new questions added Oct 2026.
50 free Calendar trivia questions with answers. Calendars look boring until you notice how much arguing, politics and astronomy went into them. This quiz covers the whole story: Julius Caesar's 46 BC reform and the astronomer behind it, the ten days Pope Gregory XIII deleted in 1582, the eleven Britain lost in 1752, why September means 'seven', which gods hide inside Tuesday and Wednesday, and the leap-year rule that made 1900 an ordinary year. It then heads abroad: the Chinese lunisolar year and its zodiac race, the Hebrew and Islamic calendars, the Maya Long Count and the 2012 fuss, the French Republican ten-day week, Ethiopia's 13 months, Kodak's 13-month year, leap seconds, the date line, and John Conway's Doomsday trick. Easy questions suit anyone who has ever wondered why February is short; the hard ones are for people who know what a bʼakʼtun is. Every answer was checked against Wikipedia's articles on the calendars, reforms and people involved, and each question carries the sentence that supports it.
30 of 100 questions with answers and explanations. Play the quiz
Q 01Which Roman leader proposed the calendar reform of 46 BC that replaced the earlier Roman calendar?
Julius Caesar
The reform took effect on 1 January 45 BC and gave the year 365.25 days on average.
Q 02Which Alexandrian astronomer is considered the principal designer of the Julian calendar?
Sosigenes
Pliny credits him; he may also have written the astronomical almanac Caesar published to help people use the new calendar.
Q 03Which pope issued the 1582 bull Inter gravissimas that reformed the calendar?
Gregory XIII
The bull was dated 24 February 1582 and the new calendar took effect that October.
Q 04How many days were skipped in October 1582 when the reformed calendar took effect?
10
Thursday 4 October 1582 was followed directly by Friday 15 October, and the weekday cycle was left unbroken.
Q 05Which Calabrian doctor's proposal, after modification, became the basis of the 1582 calendar reform?
Aloysius Lilius
He died in 1576, so his brother Antonio presented the plan in Rome; the 'Lilian date' in computing counts days from 15 October 1582 in his honour.
Q 06What is the average length of a year in the Gregorian calendar?
365.2425 days
That is 365 days, 5 hours, 49 minutes and 12 seconds; the calendar gains only about 0.1 day on the sun every 400 years.
Q 07Under the Gregorian rules, which of these years was NOT a leap year?
1900
Centurial years are leap years only if divisible by 400, so 1700, 1800 and 1900 all skipped 29 February.
Q 08In September 1752, Wednesday the 2nd in Britain and its colonies was followed directly by which day?
Thursday the 14th
Eleven days vanished; rents and wages were prorated so nobody gained or lost by the change.
Q 09Britain's 1750 calendar act is also known by the name of which lord who introduced it?
Chesterfield
It was a private member's bill; the prime minister opposed it because he 'did not love new-fangled things'.
Q 10Which satirist's painting An Election Entertainment underpins the 'Give us our eleven days!' riot myth?
William Hogarth
The only other source is a satirical journal run by the very lord who introduced the bill.
Q 11When Soviet Russia switched to the Gregorian calendar in February 1918, how many days were dropped?
13
Wednesday 31 January was followed by Thursday 14 February, and Julian dates had to be written in brackets until July.
Q 12Which country's calendar contained a 30 February in 1712?
Sweden
It had skipped a leap day in 1700 planning a gradual switch, then gave up and gave 1712 two leap days to get back onto the Julian calendar.
Q 13When the US took over Alaska in October 1867, Saturday the 7th (Julian) became which Gregorian date?
Friday the 18th
The territory crossed the date line at the same time as it changed calendars, so the weekday went backwards; the anniversary is now Alaska Day.
Q 21Wednesday takes its name from which Germanic god?
Woden
He is Óðinn to the North Germanic peoples; the day corresponds to the Roman day of Mercury.
Q 22Under the ISO 8601 standard, which day is treated as the first day of the week?
Monday
Many countries still count it as the second day, following the older Sunday-first tradition.
Q 23In the ISO week-date system, week 1 of a year is defined as the week containing the year's first what?
Thursday
Equivalently, it is always the week that contains 4 January.
Q 24How many years in every 400-year cycle have a 53rd ISO week?
Q 14The legendary calendar of Romulus had ten months and began in spring with which month?
March
Winter was simply left as an unassigned stretch of days before the next year began.
Q 15Which Roman king is traditionally credited with adding the months of January and February?
Numa Pompilius
The addition, around 713 BC, brought the calendar up to a 354-day lunar year.
Q 16January is named after which Roman god?
Janus
He is the god of beginnings and transitions, and the Saxons instead called the month Wulf-monath, 'wolf month'.
Q 17Before it was renamed in 44 BC to honour a Roman statesman born in it, July was known by which name?
Quintilis
The name meant 'fifth', since the year once began in March.
Q 18Which 13th-century scholar invented the tale that Augustus stole a day from February?
Johannes de Sacrobosco
Sextilis already had 31 days before it was renamed in 8 BC.
Q 19September's name comes from the Latin word for which number?
Seven
It was the seventh month of the old Roman year, which is also why October, November and December are off by two.
Q 20Which day of the week is named after Tiw, a one-handed Germanic god of single combat and pledges?
Tuesday
He is the Norse Týr, and his day maps onto the Roman day of Mars.
71
They are the years containing 53 Thursdays; the ISO year can start as early as 29 December.
Q 25The traditional Chinese calendar is which type of calendar?
Lunisolar
Months start on the new moon, and a year has 12 or 13 of them so it stays roughly in step with the sun.
Q 26According to legend, which animal won the Jade Emperor's race and got the first year of the zodiac cycle?
Rat
The Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog and Pig follow.
Q 27In Hebrew leap years, the 12th and 13th months are both known by what name?
Adar
Leap months come seven times in every 19-year Metonic cycle, and sources disagree on which of the two is the 'real' one.
Q 28How many days are in a year of the Islamic (Hijri) lunar calendar?
354 or 355
Because it is about 11 days short of the solar year, Ramadan drifts through all four seasons over roughly 33 years.
Q 29The Islamic era's epoch is the year Muhammad migrated from Mecca to Medina; in which year CE was that?
622
The migration is the Hijrah, and years are written AH, from the Latin Anno Hegirae.
Q 30Which caliph introduced a numbered Muslim era around 638 CE after an official complained letters had no year?
Umar
The complaint came from Abu Musa al-Ash'ari in Basra, who could not tell which instructions were most recent.