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Yes. It sits on the Technology 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.

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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.

Mondo Knows Facts

Clocks are nudged to follow the spinning Earth

Since 1972 the time signal has been stepped by a second now and then, because the planet does not keep perfect time Atomic clocks are steady, but Earth's rotation wobbles and slowly slows, so the two measures drift apart. The International Earth Rotation Service announces a leap second when the gap approaches 0.9 seconds, and one has been added 27 times, always at the end of June or December. The most recent was at the close of 2016, and none have been negative so far. It sits in Mondo's technology collection, one of 200 facts that each trace back to the reference below.

Where this comes from

International Earth Rotation and Reference Systems Service

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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Computers set their clocks through a server hierarchyThe Network Time Protocol assigns each time source a stratum number, and each level takes its time from the one above Unix time counts the seconds elapsed since 1 January 1970Computers use the Unix epoch as a standardized reference point for tracking system time Coordinated Universal Time replaced Greenwich Mean TimeThe new standard relies on atomic clocks rather than the rotation of the Earth Quartz clocks keep time by measuring vibrations in a crystalWarren Marrison built the first quartz crystal clock at Bell Telephone Laboratories in 1927 GPS clocks tick faster in orbitSatellite clocks gain about 38 microseconds a day from weaker gravity and their orbital speed combined The ISO standards body began in 1947Delegates from twenty five countries set up the organisation in Geneva to agree technical standards across borders

Tags: time, clocks, standards

Clocks are nudged to follow the spinning Earth: the short answers

Where does this come from, and can I check it?: Since 1972 the time signal has been stepped by a second now and then, because the planet does not keep perfect time. The figure is taken from International Earth Rotation and Reference Systems Service, 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 technology fact?: Yes. It sits on the Technology 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.