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41-466: The Alaska Time Zone observes standard time by subtracting nine hours from Coordinated Universal Time ( UTC−09:00 ). During daylight saving time its time offset is eight hours ( UTC−08:00 ). The clock time in this zone is based on mean solar time at the 135th meridian west of the Greenwich Observatory . The zone includes nearly all of the U.S. state of Alaska and is one hour behind

82-492: A nationwide standard time. A telegraph cable between New Zealand's two main islands became the instigating factor for the establishment of "New Zealand time". In 1868, the Telegraph Department adopted " Wellington time" as the standard time across all their offices so that opening and closing times could be synchronised. The Post Office, which usually shared the same building, followed suit. However, protests that time

123-479: Is "improper" based on the Latin meaning (a.m. stands for ante meridiem and p.m. for post meridiem , meaning "before midday" and "after midday" respectively), digital clocks are unable to display anything else, and an arbitrary decision must be made. An earlier standard of indicating noon as "12M" or "12m" (for "meridies"), which was specified in the U.S. GPO Government Style Manual , has fallen into relative obscurity;

164-419: Is one solar hour behind the legal time zone and observes daylight saving time as well for a two-hour discrepancy between legal time and solar time. Some local residents refer to this phenomenon as "double daylight time". In Fairbanks , the same circumstances cause sunset to occur at 12:47 a.m. the next calendar day and the solar sunset is at 10:47 p.m. Even without daylight saving time, another anomaly

205-832: Is that on the winter solstice in Nome , the sunrise is after "noon" clock time, at 12:02 p.m., about 4 hours before sunset at 3:56 p.m. The territory of the state of Alaska spans almost as much longitude as the contiguous United States (57.5° vs. 57.6°) so the use of only two time zones will inevitably lead to some distortions. Alaska would naturally fall into five time zones, with the greatest territory more correctly in UTC−10:00 and UTC−11:00, with Adak more correctly in UTC–12:00 and Cape Wrangell in UTC–13:00 as sunset can be late as midnight . But political and logistical considerations have led to

246-543: The Colonial Time Service Observatory in Wellington, determined the correct time each morning. At 9 a.m. each day, it was transmitted by Morse code to post offices and railway stations around the country. In 1920, radio time signals began broadcasting, greatly increasing the accuracy of the time nationwide. Solar noon The word noon is derived from Latin nona hora , the ninth canonical hour of

287-539: The Pacific Time Zone . The western Aleutian Islands observe Hawaii–Aleutian Time , one hour behind the remainder of the state. The largest city in the Alaskan Time Zone is Anchorage, Alaska . The Anchorage Metropolitan Area is the largest metropolitan area in the zone. Effective from 2007, the local time changes from AKST to AKDT at 02:00 LST (local standard time) to 03:00 LDT (local daylight time) on

328-514: The contiguous United States , based upon Greenwich Mean Time . The General Time Convention (renamed the American Railway Association in 1891), an organization of US railroads charged with coordinating schedules and operating standards, became increasingly concerned that if the US government adopted a standard time scheme it would be disadvantageous to its member railroads. William F. Allen,

369-478: The current epoch are centered on 11 February, 13 May, 26 July, and 3 November. It occurs at only one particular line of longitude in each instance. This line varies year to year, since Earth's true year is not an integer number of days. This event time and location also varies due to Earth's orbit being gravitationally perturbed by the planets. These four 24-hour days occur in both hemispheres simultaneously. The precise UTC times for these four days also mark when

410-460: The solar time at the extreme westerly points of the Alaskan time zone will be only 8:42 a.m., nearly 3 hours and 18 minutes behind clock time. Very few people notice this, however, as these locations are virtually uninhabited, and for the very few people who do live there, the long days in the summer and short days in the winter make the sunrise and sunset times less important than areas closer to

451-680: The "Allegheny Time" system, an astronomical timekeeping service which had been developed by Samuel Pierpont Langley at the University of Pittsburgh 's Allegheny Observatory (then known as the Western University of Pennsylvania , located in Pittsburgh, Pennsylvania ). Instituted in 1869, the Allegheny Observatory's service is believed to have been the first regular and systematic system of time distribution to railroads and cities as well as

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492-624: The 60th meridian west of Greenwich, instead adopting Eastern Time, so only four time zones were actually adopted by U.S./Canadian railroads in 1883. Major American observatories, including the Allegheny Observatory, the United States Naval Observatory , the Harvard College Observatory , and the Yale University Observatory , agreed to provide telegraphic time signals at noon Eastern Time. Standard time

533-522: The Alaska Time Zone are off by up to 169°30′ − 135° = 34°30′ from local solar time, or slightly more than 2 hours and 17 minutes. At noon Alaskan Time at a location just east of 169°30′ W, local solar time is only about 9:42 a.m. The sun will not reach culmination for another 2 hours and 18 minutes. When UTC−08:00 is applied in the summer (because of daylight saving time ), this effect becomes even more apparent. For example, on June 12 at noon AKDT,

574-615: The Convention secretary, argued that North American railroads should adopt a five-zone standard, similar to the one in use today, to avoid government action. On October 11, 1883, the heads of the major railroads met in Chicago at the Grand Pacific Hotel and agreed to adopt Allen's proposed system. The members agreed that on Sunday, November 18, 1883, all United States and Canadian railroads would readjust their clocks and watches to reflect

615-582: The Tropic of Cancer, the Sun is due south of the observer at solar noon; in the Southern Hemisphere , south of the Tropic of Capricorn, it is due north. The elapsed time from the local solar noon of one day to the next is exactly 24 hours on only four instances in any given year. This occurs when the effects of Earth's obliquity of ecliptic and its orbital speed around the Sun offset each other. These four days for

656-472: The day, in reference to the Western Christian liturgical term Nones (liturgy) , (number nine), one of the seven fixed prayer times in traditional Christian denominations . The Roman and Western European medieval monastic day began at 6:00 a.m. (06:00) at the equinox by modern timekeeping, so the ninth hour started at what is now 3:00 p.m. (15:00) at the equinox. In English, the meaning of

697-678: The east of the country, this was a few minutes earlier than in the west. After that, all parts of the country had the same local time—that of the Wester Tower in Amsterdam (Westertoren/4°53'01.95" E). This time was indicated as GMT +0h 19m 32.13s until 17 March 1937, after which it was simplified to GMT+0h20m. This time zone was also known as the Loenen time or Gorinchem time , as this was the exact time in both Loenen and Gorinchem . At noon in Amsterdam, it

738-493: The equator. By contrast, in Juneau, which is much closer to the 135° west meridian, mean solar noon occurs around 11:57 a.m., very close to noon on the clock. In Anchorage , visitors from more southerly latitudes are often surprised to see the sun set at 11:41 p.m. on the summer solstice while the solar time is 9:41 p.m. Anchorage is at 150° W , one hour further west from the solar time for UTC−09:00. Thus, Anchorage

779-686: The horizon on that day and casting the shortest shadow. This is also the origin of the terms ante meridiem (a.m.) and post meridiem (p.m.), as noted below. The Sun is directly overhead at solar noon at the Equator on the equinoxes , at the Tropic of Cancer ( latitude 23°26′09.8″ N) on the June solstice and at the Tropic of Capricorn (23°26′09.8″ S) on the December solstice . In the Northern Hemisphere , north of

820-530: The inseparable correspondence between longitude and time , solidified the concept of halving the globe into the Eastern Hemisphere and the Western Hemisphere , with one Prime Meridian replacing the various prime meridians that had previously been used. During the 19th century, scheduled steamships and trains required time standardisation in the industrialized world. A standardised time system

861-518: The interior was on UTC−10:00. Nome and the Aleutians previously observed Bering Standard Time or UTC−11:00 . In 1975, the Yukon Territory switched to Pacific Standard Time, leaving Yakutat the only land area in the zone. With the consolidation of Alaska's four time zones into two in 1983, the entire state was in either a zone based on UTC−09:00 or UTC−10:00. The Yukon Time Zone based on UTC−09:00

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902-470: The liberation of the Netherlands in 1945, Summer time was abolished for over thirty years, so during those years, standard time was 40 minutes ahead of the original Amsterdam Time. As of 2017, the Netherlands is in line with Central European Time (GMT+1 in the winter, GMT+2 in the summer, which is significantly different from Amsterdam Time). In 1868, New Zealand was the first country in the world to establish

943-645: The meridian through Washington, DC for North American railroads. In 1872 he revised his proposal to base it on the Greenwich meridian . Sandford Fleming , a Scottish-born Canadian engineer, proposed worldwide Standard Time at a meeting of the Royal Canadian Institute on February 8, 1879. Cleveland Abbe advocated standard time to better coordinate international weather observations and resultant weather forecasts , which had been coordinated using local solar time . In 1879 he recommended four time zones across

984-620: The meridians anchoring the Atlantic Time Zone and the Greenland Time Zone , voted in 1935 to create a half-hour offset time zone known as the Newfoundland Time Zone , at three and a half hours behind Greenwich time. In the Netherlands, introduction of the railways made it desirable to create a standard time. On 1 May 1909, Amsterdam Time or Dutch Time was introduced. Before that, time was measured in different cities; in

1025-534: The new five-zone system on a telegraph signal from the Allegheny Observatory in Pittsburgh at exactly noon on the 90th meridian. Although most railroads adopted the new system as scheduled, some did so early on October 7 and others late on December 2. The Intercolonial Railway serving the Canadian maritime provinces of New Brunswick and Nova Scotia just east of Maine decided not to adopt Intercolonial Time based on

1066-567: The opposite line of longitude, 180° away, experiences precisely 24 hours from local midnight to local midnight the next day. Thus, four varying great circles of longitude define from year to year when a 24-hour day (noon to noon or midnight to midnight) occurs. The two longest time spans from noon to noon occur twice each year, around 20 June (24 hours plus 13 seconds) and 21 December (24 hours plus 30 seconds). The shortest time spans occur twice each year, around 25 March (24 hours minus 18 seconds) and 13 September (24 hours minus 22 seconds). For

1107-627: The origin of the modern standard time system. By 1870 the Allegheny Time service extended over 2,500 miles with 300 telegraph offices receiving time signals. However, almost all railroads out of New York ran on New York time, and railroads west from Chicago mostly used Chicago time, but between Chicago and Pittsburgh/Buffalo the norm was Columbus time, even on railroads such as the PFtW&;C and LS&MS , which did not run through Columbus. The Santa Fe Railroad used Jefferson City (Missouri) time all

1148-672: The role of the Secretary of Commerce (effectively, the National Institute of Standards and Technology ) and the Secretary of the Navy (effectively, the U.S. Naval Observatory ) in interpreting standard time. In 1999, standard time was inducted into the North America Railway Hall of Fame in the category "National: Technical Innovations." The Dominion of Newfoundland , whose capital St. John's falls almost exactly midway between

1189-459: The same reasons, solar noon and "clock noon" are usually not the same. The equation of time shows that the reading of a clock at solar noon will be higher or lower than 12:00 by as much as 16 minutes. Additionally, due to the political nature of time zones, as well as the application of daylight saving time , it can be off by more than an hour. In the US, noon is commonly indicated by 12 p.m., and midnight by 12 a.m. While some argue that such usage

1230-503: The second Sunday in March and returns at 02:00 LDT to 01:00 LST on the first Sunday in November. As such, Alaska spends most of the year on daylight saving time rather than standard time. Two time zones have been referred to as the "Alaska Time Zone": a zone based on UTC−10:00 that covered much of Central Alaska in the early 20th century, and a zone based on UTC−09:00 zone that has covered all of

1271-670: The state except the Aleutian Islands since 1983. The Standard Time Act of 1918 authorized the Interstate Commerce Commission to define each time zone. The United States Standard Alaska Time was designated as UTC−10:00. Some references prior to 1967 refer to this zone as Central Alaska Standard Time (CAT) or as Alaska Standard Time (AST). In 1966, the Uniform Time Act renamed the UTC−10:00 zone to Alaska-Hawaii Standard Time (AHST), effective April 1, 1967. This zone

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1312-418: The use of two time zones, leading to the distortions mentioned above. Standard time Standard time is the synchronization of clocks within a geographical region to a single time standard, rather than a local mean time standard. Generally, standard time agrees with the local mean time at some meridian that passes through the region, often near the centre of the region. Historically, standard time

1353-544: The way to its west end at Deming, New Mexico , as did the east–west lines across Texas; Central Pacific and Southern Pacific Railroads used San Francisco time all the way to El Paso . The Northern Pacific Railroad had seven time zones between St. Paul and the 1883 west end of the railroad at Wallula Jct ; the Union Pacific Railway was at the other extreme, with only two time zones between Omaha and Ogden. In 1870, Charles F. Dowd proposed four time zones based on

1394-490: The word shifted to midday and the time gradually moved back to 12:00 local time – that is, not taking into account the modern invention of time zones. The change began in the 12th century and was fixed by the 14th century. Solar noon , also known as the local apparent solar noon and Sun transit time (informally high noon ), is the moment when the Sun contacts the observer's meridian ( culmination or meridian transit ), reaching its highest position above

1435-535: Was 11:40 in London and 12:40 in Berlin . The shift to the current Central European Time zone took place on 16 May 1940. The German occupiers ordered the clock to be moved an hour and forty minutes forward. This time was kept in summer and winter throughout 1941 and 1942. It was only in November 1942 that a different Winter time was introduced, and the time was adjusted one hour backwards. This lasted for only three years; after

1476-504: Was being dictated by one government department, led to a resolution in parliament to establish a standard time for the whole country. The director of the Geological Survey, James Hector , selected New Zealand time to be at the meridian 172°30′E. This was very close to the country's mean longitude and exactly 11 + 1 ⁄ 2 hours in advance of Greenwich Mean Time. It came into effect on 2 November 1868. For over fifty years,

1517-400: Was established during the 19th century to aid weather forecasting and train travel. Applied globally in the 20th century, the geographical regions became time zones . The standard time in each time zone has come to be defined as an offset from Universal Time . A further offset is applied for part of the year in regions with daylight saving time . The adoption of standard time, because of

1558-477: Was first used by British railways on 1 December 1847, when they switched from local mean time, which varied from place to place, to Greenwich Mean Time (GMT). It was also given the name railway time , reflecting the important role the railway companies played in bringing it about. The vast majority of Great Britain's public clocks were standardised to GMT by 1855. Until 1883, each United States railroad chose its own time standards. The Pennsylvania Railroad used

1599-410: Was later renamed the Alaska Time Zone in 1984. The Alaska Time Zone applies to the territory of the state of Alaska east of 169°30′ W, that is, the entire state minus the westernmost portions of the Aleutian Islands. Solar time zones are 15° wide. UTC−09:00 time corresponds to the solar time at 9 × 15° = 135° W (roughly, Juneau , which is in the southeast panhandle). Thus, the westernmost locales of

1640-427: Was not enacted into US law until the 1918 Standard Time Act established standard time in time zones; the law also instituted daylight saving time (DST). The daylight saving time portion of the law was repealed in 1919 over a presidential veto, but was re-established nationally during World War II. In 2007 the US enacted a federal law formalising the use of Coordinated Universal Time as the basis of standard time, and

1681-479: Was renamed in 1983 to Hawaii–Aleutian Standard Time when the majority of Alaska was moved out of the zone. Prior to 1983, the current Alaska Time Zone (UTC−09:00) was known as the Yukon Time Zone , observing Yukon Standard Time (YST). This time zone included Canada's Yukon Territory and a small portion of Alaska including Yakutat . The Alaska Panhandle communities were in the Pacific Time Zone , while most of

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