<P> Greenwich Mean Time (GMT) was established in 1675, when the Royal Observatory was built, as an aid to mariners to determine longitude at sea, providing a standard reference time while each city in England kept a different local time . </P> <P> Local solar time became increasingly inconvenient as rail transport and telecommunications improved, because clocks differed between places by amounts corresponding to the differences in their geographical longitudes, which varied by four minutes of time for every degree of longitude . For example, Bristol is about 2.5 degrees west of Greenwich (East London), so when it is solar noon in Bristol, it is about 10 minutes past solar noon in London . The use of time zones accumulates these differences into longer units, usually hours, so that nearby places can share a common standard for timekeeping . </P> <P> The first adoption of a standard time was on December 1, 1847, in Great Britain by railway companies using GMT kept by portable chronometers . The first of these companies to adopt standard time was the Great Western Railway (GWR) in November 1840 . This quickly became known as Railway Time . About August 23, 1852, time signals were first transmitted by telegraph from the Royal Observatory, Greenwich . Even though 98% of Great Britain's public clocks were using GMT by 1855, it was not made Britain's legal time until August 2, 1880 . Some British clocks from this period have two minute hands--one for the local time, one for GMT . </P> <P> Improvements in worldwide communication further increased the need for interacting parties to communicate mutually comprehensible time references to one another . The problem of differing local times could be solved across larger areas by synchronizing clocks worldwide, but in many places that adopted time would then differ markedly from the solar time to which people were accustomed . </P>

When did the first country adopted time zones