Time zones follow borders more than neat meridians
A time zone is a region sharing one legal standard time for commerce and daily life. Offsets from UTC stretch from −12:00 to +14:00, usually whole hours, with a few half- or quarter-hour exceptions—and lines kink around politics.
A time zone is an area keeping one standard time for legal, business, and social life, and its borders usually follow national or regional boundaries rather than strict lines of longitude, because neighbours who deal with each other want matching clocks. Solar time shifts four minutes for each degree of longitude, so solar noon in Bristol comes about ten minutes after London's. India and Nepal are among the few places offset by an extra 30 or 45 minutes, and China and India each use a single zone despite spanning far more.
Greenwich Mean Time began at the Royal Observatory, founded in 1675, as a reference to help sailors find longitude while every English town kept its own hour. Railways forced the change: the Great Western Railway adopted GMT in November 1840, carrying it by portable chronometer, telegraph time signals went out from Greenwich around 23 August 1852, and by 1855 almost all public clocks in Britain used GMT, though it became legal time only on 2 August 1880. On 2 November 1868 New Zealand set a colony-wide standard 11 hours 30 minutes ahead of GMT.
North American railroads each kept their own time, and some junctions displayed a clock for every line. Charles F. Dowd proposed hourly zones around 1863, the meteorologist Cleveland Abbe divided the country into four zones for weather stations and published a Report on Standard Time in 1879, and in 1883 the railroads adopted a scheme by William F. Allen, with borders running through stations in cities such as Detroit and Pittsburgh. Within a year about 200 larger cities had signed on, though Detroit clung to local time.
The Italian Quirico Filopanti imagined 24 worldwide zones centred on Rome in his 1858 book Miranda!, and in 1876 Sandford Fleming proposed 24 lettered zones each 15 degrees wide. By about 1900 nearly every inhabited place had a standard time. Under ISO 8601 a UTC time takes the suffix Z, for Zulu, so 09:30 UTC is 09:30Z, and other offsets appear as forms like +01:00.
Source: Time zone
