Mondo Knows Facts
The 24-hour day comes from Earth's rotation
The division into 24 hours is ancient, but the length of the day is not perfectly constant Babylonian astronomers used a base-60 system that survived into the hours and minutes we still write. The actual rotation period wobbles slightly with the movement of air, water and the core. Because of that, astronomical time and clock time have to be reconciled with occasional adjustments. It sits in Mondo's world geography collection, one of 200 facts that each trace back to the reference below.
Where this comes from
Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.
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More facts like this
Time zones follow politics more than the SunSeveral countries use offsets that sit far from their solar time, and some use half-hour stepsChina keeps one clock across five time zonesOfficial time in Beijing applies from the eastern coast to Xinjiang, nearly 5,000 kilometres westNepal's clock runs 45 minutes off the hourIts offset of five hours and 45 minutes is one of the oddest in the worldCoordinated Universal Time replaced Greenwich Mean TimeThe new standard relies on atomic clocks rather than the rotation of the EarthThe International Date Line is not a straight lineIt zigzags around countries so that no single state has to keep two calendar datesDamascus is widely cited as the world oldest continuously inhabited capitalEvidence of urban settlement at Damascus in Syria dates back more than four thousand years.
🗺️ World Geographyfact 185 of 200
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Tags: time-zones, clocks, history
The 24-hour day comes from Earth's rotation: the short answers
- Where does this come from, and can I check it?
- The division into 24 hours is ancient, but the length of the day is not perfectly constant. The figure is taken from Royal Museums Greenwich, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
- Is this really a world geography fact?
- Yes. It sits on the World Geography shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
- What else can I read about it?
- The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.