Calendars and clocks quiz
Checked on 4 November 2026
Question 1 of 10
Discover
Greenwich Mean Time is the local mean time at the Royal Observatory in Greenwich. Which city is Greenwich part of?
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The answer is London.
Greenwich Mean Time (GMT) is the local mean time at the Royal Observatory in Greenwich, London, counted from midnight.
Discover
How many seconds are there in one hour?
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The answer is 3,600.
An hour is 60 minutes of 60 seconds each, so it is defined as exactly 3,600 seconds.
Discover
In a leap year, which month gets an extra day?
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The answer is February.
In a leap year February has 29 days instead of the usual 28.
Discover
In the knuckle trick for remembering month lengths, months that land on a knuckle have how many days?
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The answer is 31.
Counting the months across your knuckles and the gaps between them, every month that lands on a knuckle has 31 days.
Practise
Which of these years was NOT a leap year?
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The answer is 1900.
Century years are leap years only if they divide by 400, so 1900 was not a leap year while 1600 and 2000 were.
Practise
On an analogue wristwatch, what is the small knob used to set the time called?
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The answer is Crown.
The crown is the small knob on the side of an analogue watch used to adjust the time and, in mechanical watches, to wind the spring.
Practise
The International Date Line mostly runs through which ocean?
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The answer is Pacific Ocean.
The International Date Line passes through the Pacific Ocean, roughly following the 180 degree line of longitude.
Expert
Unix time, used by many computers, counts seconds from which starting date?
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The answer is 1 January 1970.
Unix time counts the seconds elapsed since 00:00:00 UTC on 1 January 1970, a moment known as the Unix epoch.
Expert
In which year was the leap second introduced?
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The answer is 1972.
Leap seconds, occasional one second adjustments that keep clock time in step with the Earth's rotation, were introduced in 1972.
Expert
At what frequency does the quartz crystal vibrate in nearly all quartz watches?
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The answer is 32,768 Hz.
Nearly all quartz clocks and watches use a crystal vibrating at 32,768 Hz, a power of two that is easy to divide down to one tick per second.