Time Standards

Today we're used to a standardised time system. We happily adjust for diferent time zones, but apart from that we expect standardisation. I know that if it's 19:03 here in Edinburgh then it will be 19:03 in London. It didn't used to be like that.

Local Time

Time of day used to be a much more local idea. This was a simple matter of practicality - there was no way to synchronise time across different towns, let alone different countries. The best that could be done was to use the sun and set noon when it was at its peak. This produced "local time", which varied from town to town because of the difference in the sun reaching the noon position. Different towns thus ran on slightly different local times - for instance, Leeds time was over six minutes behind London time. As clock and watch technology improved these differences became more obvious, especially to travellers.

Railway Time

The change didn't come until the mid-nineteenth century and the arrival of new technology, in particular the railways and the telegraph.

The first really standard time was introduced into the UK by the railways. In 1840 the Great Western Railway officially adopted "London time" - what we now know as Greenwich Mean Time (GMT). Other railways followed suit over the next decade.

By the 1850s most public clocks in Britain were showing GMT and it was the de facto standard. It became a formal standard in 1880 with the passing of the "Statutes (Definition of Time) Act".

UTC - Zulu Time

More modern timekeeping still - in particular the atomic clock - has resulted in the current time standard: Coordinated Universal Time (UTC). This was offically introduced in 1972.

An atomic clock is highly accurate, however atomic time is slightly faster than earth time. As a result, atomic time will gradually drift out of synchronisation with GMT. UTC thus uses atomic clocks to measure the rate of time and adjusts the absolute time when necessary to keep UTC within 0.9 seconds of GMT. This adjustment is known as a "leap second".

The nautical GMT timezone is designated by the letter "Z", which is "Zulu" in the phoenetic alphabet. GMT/UTC is thus sometimes called Zulu Time.

	All About Clocks, Watches and Time
Time Standards Today we're used to a standardised time system. We happily adjust for diferent time zones, but apart from that we expect standardisation. I know that if it's 19:03 here in Edinburgh then it will be 19:03 in London. It didn't used to be like that. Local Time Time of day used to be a much more local idea. This was a simple matter of practicality - there was no way to synchronise time across different towns, let alone different countries. The best that could be done was to use the sun and set noon when it was at its peak. This produced "local time", which varied from town to town because of the difference in the sun reaching the noon position. Different towns thus ran on slightly different local times - for instance, Leeds time was over six minutes behind London time. As clock and watch technology improved these differences became more obvious, especially to travellers. Railway Time The change didn't come until the mid-nineteenth century and the arrival of new technology, in particular the railways and the telegraph. The first really standard time was introduced into the UK by the railways. In 1840 the Great Western Railway officially adopted "London time" - what we now know as Greenwich Mean Time (GMT). Other railways followed suit over the next decade. By the 1850s most public clocks in Britain were showing GMT and it was the de facto standard. It became a formal standard in 1880 with the passing of the "Statutes (Definition of Time) Act". UTC - Zulu Time More modern timekeeping still - in particular the atomic clock - has resulted in the current time standard: Coordinated Universal Time (UTC). This was offically introduced in 1972. An atomic clock is highly accurate, however atomic time is slightly faster than earth time. As a result, atomic time will gradually drift out of synchronisation with GMT. UTC thus uses atomic clocks to measure the rate of time and adjusts the absolute time when necessary to keep UTC within 0.9 seconds of GMT. This adjustment is known as a "leap second". The nautical GMT timezone is designated by the letter "Z", which is "Zulu" in the phoenetic alphabet. GMT/UTC is thus sometimes called Zulu Time. Clocks-Watches-Time / Time / Standard / All original material copyright © Trevor Mendham 2005-2008. All trademarks are the property of their respective owners Please read the site terms of use		Clocks Watches Time 60 24 Hours 7 Days Arrow Atomic Bells Biological Calendars Daylight Saving Leap Seconds Planck Quotes Solar Standard Travel Zones Time & Motion More...