Country Selection You visit the website of another country. Please note that we only deliver to addresses in this country. Language Selection Select language of country. Select language English Germany Deutsch Deutschland. Select language English United Kingdom. Select language English. Home Share this page. What is a GMT Watch? What does GMT stand for? However, the s and s saw the expansion of the railway and communications networks.
This meant the need for an national time standard became imperative. British railway companies started introducing a single standard time across their networks, designed to make their timetables less confusing. It was mostly Greenwich Mean Time that they used. It officially became 'Railway Time'.
There were two main reasons for this. The first was that the USA had already chosen Greenwich as the basis for its own national time zone system. As the reference for GMT, the Prime Meridian at Greenwich therefore became the centre of world time and the basis for the global system of time zones.
Therefore this also became the start of the Universal Day. The meridian line is marked by the cross-hairs in the Airy Transit Circle eyepiece. Find out more about the Airy Transit Circle. The Shepherd gate clock can be seen at the gates to the Royal Observatory.
It was the first clock ever to show Greenwich Mean Time directly to the public. It is a 'slave' clock, connected to the Shepherd master clock which was installed at the Royal Observatory in From that time until , the Shepherd master clock was the heart of Britain's time system.
Its time was sent by telegraph wires to London, Edinburgh, Glasgow, Dublin, Belfast and many other cities. By , time signals were also sent from the clock to Harvard University in Cambridge, Massachusetts via the new transatlantic submarine cable. In terms of the distribution of accurate time into everyday life, it is one of the most important clocks ever made. The first thing you notice about the clock is that it has 24 hours on its face rather than the usual That means at 12 noon the hour hand is pointing straight down rather than straight up.
The clock originally indicated astronomical time, in which the counting of the 24 hours of each day starts at noon. The second hour hand often runs on a hour clock rather than 12 to improve ease of use. This usually involves adding two extra wheels to the mechanism.
They typically comprise a hour track located along the bezel or outside of the dial, which can be fixed or rotating. In both cases, the time zones are referred to as current time where the wearer is and home time where the wearer is based. Both complications hark back to the s and 50s, when the need for such models was brought about by the rise in commercial air travel.
As flying distances increased, and more flights traversed several time zones, pilots required a timepiece that could track GMT along with local time. Launched in , the Rolex GMT-Master featured a long hour hand that made one revolution around the dial every 24 hours and pointed to a bezel marked with 24 hour increments, as well as a short hour hand which could be independently set on a hour scale to follow local time. However, this cracked easily, so Rolex switched to aluminium instead.
A simple arrow-tipped hand rotates around the dial once a day and points to home time, which is read off the hour bezel.
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