Which railway adopted Greenwich Mean Time in 1840, helping spread standard time?

The Great Western Railway adopted Greenwich Mean Time in 1840, helping spread standard time. In November 1840, the railway aligned its timetable and station clocks with London time, based on the Royal Observatory at Greenwich.

Before railway time, towns set clocks by local solar time. Bristol, for example, was several minutes behind London, while Leeds was about six minutes behind. Those small differences created confusion for passengers and complicated timetables on a rapidly expanding railway network.

Other British railway companies followed during the 1840s. The Midland Railway adopted London Time in 1846, and in 1847 the Railway Clearing House urged all stations to use GMT. By 1855, most British towns and cities had shifted to Greenwich time, although legal nationwide standardisation came only with the Statutes (Definition of Time) Act in 1880.

A common mix-up is crediting the 1880 law as the beginning of standard time. The Great Western Railway’s 1840 change came decades earlier and was one of the earliest large-scale uses of a single standard time.