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Some junctions served by several railroads had a clock for each railroad, each showing a different time. Each railroad used its own standard time, usually based on the local time of its headquarters or most important terminus, and the railroad's train schedules were published using its own time.
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Timekeeping on North American railroads in the 19th century was complex. 1913 time zone map of the United States, showing boundaries very different from today This standard was known as New Zealand Mean Time. It was based on longitude 172☃0′ east of Greenwich, that is 11 hours 30 minutes ahead of GMT. On November 2, 1868, the then British Colony of New Zealand officially adopted a standard time to be observed throughout the colony. Some British clocks from this period have two minute hands, one for the local time and one for GMT. By 1855, 98% of Great Britain's public clocks were using GMT, but it was not made the island's legal time until August 2, 1880. This practice was soon followed by other railway companies in Great Britain and became known as Railway Time.Īround August 23, 1852, time signals were first transmitted by telegraph from the Royal Observatory. In November 1840, the British Great Western Railway started using GMT kept by portable chronometers. In the 19th century, as transportation and telecommunications improved, it became increasingly inconvenient for each location to observe its own solar time. Main article: Railway time Plaque commemorating the Railway General Time Convention of 1883 in North America The control panel of the Time Zone Clock in front of Coventry Transport Museum DST is usually used for about half of the year, typically by adding one hour to local time during spring and summer. The UTC offsets range from UTC−12:00 to UTC+14:00, and are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes (such as in India, South Australia and Nepal).Īreas of extreme latitude are more likely to use DST. Some time zones switch between offsets throughout the year due to daylight saving time (DST). Time zones are defined as one or two offsets from Coordinated Universal Time (UTC), and (if two offsets are used) the days when the offset changes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time. For other uses, see Time zone (disambiguation).Ī time zone is an area which observes a uniform standard time for legal, commercial and social purposes. For more time zone lists, see Lists of time zones. For a list of time zones by country, see List of time zones by country. This article is about time zones in general.