Do you know your calendar trivia?

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We use calendars to keep track of our days, our weeks and our years. But how much do we really know about them?

Question 1 of 14

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The letters B and C in ornate styles
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What does the abbreviation B.C. stand for?

It stands for "Before Christ" to denote history that occurred prior to the birth of Jesus.

Question 2 of 14

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Calendar pages
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Which months have 31 days in them?

A helpful poem may help you remember "30 days has September, April, June, and November. All the rest have 31. Save February." There's also a knuckle mnemonic you can use.

Question 3 of 14

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'I heart weekends' with a sloppy red heart
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When can you expect a month to have 5 weekends in it?

Contrary to the internet myth you may have seen on social media or in your email, months with five weekends are not rare calendar unicorns that only happen every 823 years. As Time and Date explains, "The first three weekdays of any 31-day month are repeated 5 times within that month. So, any month that has 31 days and begins on a Friday will have 5 Fridays, 5 Saturdays, and 5 Sundays. Similarly, any 31-day month that begins on a Tuesday, will have 5 Tuesdays, 5 Wednesdays and 5 Thursdays."

Question 4 of 14

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A water-stained calendar
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What holiday spurred the creation of the Gregorian calendar?

The intention of the calendar was to stop the drift associated with the spring equinox and its connection to Easter. To deal with the drift, the Gregorian calendar eliminated 10 dates in October and adjustments were made to leap years.

Question 5 of 14

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Days of the week spelled out in mechanical panels
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When a century ends, which of these days will it NOT end on?

A century cannot end on a Thursday, Sunday or Tuesday. It has to do with the cycle of odd days across 400 years. The first century in the cycle consists of five odd days, resulting in the century ending on a Friday. The next century has three odd days, with Wednesday as the last day. The third century has one odd day and ends on a Monday. The fourth century in the cycle ends on a Sunday as it has no odd days. This cycle repeats after that.

Question 6 of 14

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A calendar with a push pin on December 31
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With that in mind, what is the last day of our current century, the 21st century?

The last day of the 21st century — Dec. 31, 2100 — is a Friday.

Question 7 of 14

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An hourglass at sunset
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Which is the longest day of the year?

It's the summer solstice. On that day, the sun travels the longest path across the sky, providing more daylight.

Question 8 of 14

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The letters A nd D carved into a stone wall
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A.D. stands for 'anno Domini.' But what does 'anno Domini' mean?

It's Latin, and means "in the year of the Lord." The A.D. dating standard was developed by the monk Dionysius Exiguus in 525 A.D.; he also developed the B.C. dating standard.

Question 9 of 14

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An image of the sun just behind the Earth
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The Gregorian calendar will end up a day ahead of the actual solar year in what year?

It's the year 4909. This is because our calendar places the solar year at 365.2425 days, while the actual solar year is 365.24222 days. So every 3,327 years, we end up a day ahead.

Question 10 of 14

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A calendar with green letters and a pen
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The word 'calendar' is derived from the word 'kalendae.' To what did it refer in ancient Roman times?

Translated, "kalendae" means "the first day of the month." Which is appropriate.

Question 11 of 14

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An illustration of the inner solar system's planets' orbits around the sun
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A year is based on how long it takes the Earth to orbit the sun. What is this called?

It's a revolution. In astronomy, a rotation refers to the circular movement of a fixed object, particularly along an axis. A revolution is when an object makes a circular motion around a fixed object, like the Earth around the sun.

Question 12 of 14

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Portrait of Pope Gregory XIII
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Which of these countries was the last country to adopt the Gregorian calendar (named for Pope Gregory XIII, pictured)?

Of these, Greece was the last country to adopt the Gregorian calendar, switching from the Julian calendar in 1923.

Question 13 of 14

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Replica of the Maya calendar
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The Maya calendar had multiple cyclical calendars within it, including the Haab. How many days were on the Haab?

Just like our current Gregorian calendar, the Haab had 365 days on it. But it had more months in it than our calendar does — 18 to be exact — and 17 of those months had 20 days and one month only had five days.

Question 14 of 14

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A fortress at night
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How long is a fortnight?

More common in England and its commonwealths, a fortnight refers to a two-week period.

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