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A brief history of time keeping

For most of history, people had no desire to know the exact time — the Sun told them when it was time for breakfast or bed.

But in the 1800s, with the coming of the industrial age in Britain, that the great manufacturing centres across the country ran on different times became a serious issue

— In 1840, the Great Western Railway in England standardised times at stations. Other companies adopted “railway time”, ironing out regional differences — for instance, Leeds time was six minutes 10 seconds behind London.

— Greenwich Observatory, in London, with its reputation for accurate timekeeping for astronomical purposes, was the obvious institute to decide on a standard, or “mean” time.

From 1880 Greenwich Mean Time, based on the passage of the Sun across the sky, was adopted legally as the single time standard for the UK.

At the Washington Meridian Conference of 1884, GMT was accepted as the time standard for the world. Places that are separated eastward or westward around the world will have a different local time from each other.

— In 1955, scientists at the National Physical Laboratory in Teddington, west London, developed the first successful atomic clock.

One second is defined as the length of 9,192,631,770 energy transitions of a caesium atom. Since 1967 the timescale known as Co-ordinated Universal Time (UTC), which is based on atomic clocks, has been the world’s official time and is used for broadcasting time signals around the globe.

— Time zones can be changed. France used GMT but switched to central European time during the Second World War.

In the U.K., some have campaigned for Scotland to have a different time zone from England to make more use of daylight south of the border. — © Guardian Newspapers Limited, 2008

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