Online Encyclopedia
Time zone
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- Time Zone is also a historical computer game. There is also an Australian franchise of video arcades called Timezone .
Time zones are areas of the Earth that have adopted the same standard time. Formerly, people used local solar time (originally apparent and then mean), resulting in time differing slightly from town to town. As telecommunications improved and with the expansion of the railways this became increasingly awkward. Time zones partially rectified the problem by setting the clocks of a region to the same mean solar time. Time zones are generally centered on meridians of a longitude that is a multiple of 15° thus making neighboring time zones one hour apart. However, the one hour separation is not universal and, as the map below shows, the shapes of time zones can be quite irregular because they usually follow the boundaries of states, countries or other administrative areas.
All time zones are defined relative to Coordinated Universal Time (UTC). The reference point for Time Zones is the Prime Meridian (longitude 0°) which passes through the Royal Greenwich Observatory in Greenwich, London, England [1] http://greenwichmeantime.com/ . For this reason the term Greenwich Mean Time (GMT) is still often used (by the BBC, for example, amongst others) to denote the "base time" to which all other time zones are relative. UTC is, nevertheless, the official term for today's atomically measured time as distinct from time determined by astronomical observation as formerly carried out at Greenwich.
GMT (UTC) is, incidentally, local time at Greenwich itself only between 01:00 UTC on the last Sunday in October and 01:00 UTC on the last Sunday in March. For the remainder of the year local time is UTC + 1—known in the UK as British Summer Time (BST).
The time for a location is given relative to UTC. Some examples:
- Los Angeles, California, USA: UTC − 8 (e.g. if it is 12:00 UTC, then it is 04:00 in Los Angeles)
- Toronto, Ontario, Canada: UTC − 5 (e.g. if it is 11:00 UTC, then it is 06:00 in Toronto)
- Stockholm, Sweden: UTC + 1 (e.g. if it is 12:00 UTC, then it is 13:00 in Stockholm)
- Mumbai, India: UTC + 5.5 (e.g. if it is 13:00 UTC, then it is 18:30 in Mumbai)
- Tokyo, Japan: UTC + 9 (e.g. if it is 11:00 UTC, then it is 20:00 in Tokyo)
Where the adjustment for time zones results in a time the other side of midnight from UTC, then the date at the location is one day later or earlier. Some examples:
- Cairo, Egypt: UTC + 2 (e.g. if it is 23:00 UTC on Monday 15 March, then the time in Cairo is 01:00, Tuesday 16 March)
- Auckland, New Zealand: UTC + 12 (e.g. if it is 21:00 UTC on Wednesday 30 June, then the time in Auckland is 09:00, Thursday 1 July)
- New York, USA: UTC − 5 (e.g. if it is 02:00 UTC on Tuesday, then the time in NY is 21:00 on Monday)
- Honolulu, Hawai'i, USA: UTC − 10 (e.g. if it is 06:00 UTC on Monday 1 May, then the time in Honolulu is 20:00, Sunday 30 April)
Note: The time zone adjustment for a specific location may vary due to the use of daylight saving time.
- e.g. New Zealand which is usually UTC + 12, observes a one-hour daylight saving time adjustment during the southern hemisphere summer resulting in a local time of UTC + 13!
See also: Sidereal time Calculating local time
History
The first time zone in the world was established by British railways on December 1, 1847—Greenwich Mean Time (GMT) being hand carried on chronometers. About August 23, 1852, time signals were first transmitted by telegraph from the Royal Greenwich Observatory. 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.
On November 2, 1868, New Zealand officially adopted a standard time to be observed nationally, and was perhaps the first country to do so. It was based on the longitude 172° 30' East of Greenwich, that is 11 hours 30 minutes ahead of Greenwich Mean Time. This standard was known as New Zealand Mean Time.
Multiple time zones were first proposed by Charles F. Dowd about 1863 for American railroads as a teacher to his students. In 1870, after consulting railroad officials in 1869, he proposed four ideal time zones, the first centered on Washington, DC, but by 1872 the first was centered 75°W of Greenwich with geographic borders. American and Canadian railroads implemented their own version on Sunday, November 18, 1883, when each railroad station clock was either advanced or delayed as noon, standard time, was reached within each time zone, east to west. The zones were named Intercolonial, Eastern, Central, Mountain, and Pacific. Within one year, 85% of all cities having populations over 10,000, about 200 cities, were using standard time. A notable exception was Detroit, Michigan, which kept local time until 1900, then vacillated between Central Standard Time, Sun time, and Eastern Standard Time until it settled on EST by ordinance May 1915, ratified by popular vote August 1916. This hodgepodge was made uniform when Standard zone time was made legal by the U.S. Congress in 1918.
Time zones were first proposed for the entire world by Sir Sandford Fleming in 1876 as an appendage to the single 24-hour clock he proposed for the entire world (located at the center of the Earth and not linked to any surface meridian!). In 1879 he specified that his universal day would begin at the anti-meridian of Greenwich (now called 180°), while conceding that hourly time zones might have some limited local use. He continued to advocate his system at subsequent international conferences. In October 1884 the International Meridian Conference did not adopt his time zones because they were not within its purview. The conference did adopt a universal day of 24 hours beginning at Greenwich midnight, but specified that it "shall not interfere with the use of local or standard time where desirable." Nevertheless, most major countries had adopted hourly time zones by 1929. Even today, they have not been fully realized, with several time zones keeping a standard time that is not offset by a number of whole hours from Greenwich Mean Time.
Before 1920, all ships kept local apparent time on the high seas by setting their clocks at night or at the morning sight so that, given the ship's speed and direction, it would be 12 o'clock when the Sun crossed the ship's meridian (12 o'clock = local apparent noon). During 1917, at the Anglo-French Conference on Time-keeping at Sea, it was recommended that all ships, both military and civilian, should adopt hourly standard time zones on the high seas. Whenever a ship was within the territorial waters of any nation it would use that nation's standard time. The captain was permitted to change his ship's clocks at a time of his choice following his ship's entry into another time zone—he often chose midnight. These zones were adopted by all major fleets between 1920 and 1925 but not by many independent merchant ships until World War II.
Time on ship's clocks and in a ship's log had to be stated along with a "zone description", which was the number of hours that was to be added to zone time to obtain GMT, hence zero in the Greenwich time zone, and negative numbers from −1 to −12 for time zones to the east and positive numbers from +1 to +12 to the west (hours, minutes, and seconds for nations without an hourly offset). These signs are opposite to those given below because ships must obtain GMT from zone time, not zone time from GMT/UTC. All zones were pole-to-pole staves 15° wide except for −12 and +12, which were each 7.5° wide separated by a longitude of 180°. Unlike the zig-zagging land-based International Date Line, the nautical International Date Line follows 180° except where it is interrupted by territorial waters and the lands they border, including islands. About 1950, a letter suffix was added to the zone description, assigning Z to the zero zone, and A-M (except J) to the east and N-Y to the west (J may be assigned to local time in non-nautical applications). These were to be vocalized using a phonetic alphabet which included Zulu for GMT.
These nautical letters have been added to some time zone maps, like the map of Standard Time Zones http://aa.usno.navy.mil/faq/docs/world_tzones.html by Her Majesty's Nautical Almanac Office (NAO), which extended the letters by adding an asterisk (*) or dagger (†) for areas that do not use a nautical time zone, and a double dagger (‡) for areas that do not have a legal standard time (Greenland's ice sheet and all of Antarctica—Britain specifies UTC − 3 for the Antarctic Peninsula, but no other country recognizes that). They conveniently ignore any zone that does not have an hour or half-hour offset, so a double dagger (‡) has been co-opted for these zones below.
List of time zones and contained areas
Regions marked with an asterisk (*) observe Daylight Saving Time: add 1 hour in summer. Some zones north-south of each other in the mid Pacific differ by 24 hours in time: they have the same time of the day but differ by a full day. The two extreme time zones on Earth (both in the mid Pacific) differ by 26 hours. A particular day starts earlier in countries with a more positive UTC offset. Thus the first occurrence of a date will be in UTC + 14 and the last of the same date in UTC − 12 (at sea). Stations in Antarctica generally keep the time of their supply bases, thus both the Amundsen-Scott South Pole Station (U.S.) and McMurdo Station (U.S.) use New Zealand time (UTC + 12 southern winter, UTC + 13 southern summer). Time zone abbreviations are almost always customary, not legal—those listed here only exist in English and are somewhat arbitrary. English time zone names below generally only apply to English speaking areas. The CIA and NAO disagree on the time kept by some Russian oblasts, so both are given below—this may be due to a recent time zone change.
UTC − 12 Y
Only ships at sea within 7.5° east of 180°.
UTC − 11 X
UTC − 10 W
- Cook Islands
-
French Polynesia
- Society Archipelago including Tahiti,
- Tuamotu Archipelago, and
- Tubuai Islands
- Johnston Atoll
- Tokelau
-
United States (HST—Hawaii-Aleutian Standard Time)
-
Alaska
- Aleutian Islands (west of 169° 30' West)*
- Hawaii
-
Alaska
UTC − 9:30 V*
UTC − 9 V
-
French Polynesia
- Gambier Islands
-
United States (AKST—Alaska Standard Time)
- Alaska (most of state)*
UTC − 8 U
-
Canada (PST—Pacific Standard Time)
- British Columbia (most of province)*,
- Yukon*
- Mexico
- Pitcairn Islands
-
United States (PST—Pacific Standard Time)
- California*,
-
Idaho*
- north of the Salmon River (between the Oregon state border and the Idaho County/Lemhi County border), and
- west of the Idaho County/Lemhi County border (between the Salmon River and the Montana state border),
- Nevada (most of state)*,
- Oregon (most of state, including southern 1/5 of Malheur County)*,
- Washington*
UTC − 7 T
-
Canada (MST—Mountain Standard Time)
- Alberta*,
-
British Columbia
- northeastern (no DST)
- Most of Peace River Regional District except Fort Ware , Beatton River , Pink Mountain , Sikanni Chief , Buckinghorse River and Trutch
- southeastern*
- Regional District of East Kootenay,
- Regional District of Central Kootenay east of the Kootenay River and parts east of Kootenay Lake that are south of and including Riondel (Creston doesn't observe DST), and
- Columbia-Shuswap Regional District east of the Selkirk Mountains,
- northeastern (no DST)
- Northwest Territories*,
-
Nunavut*
- west of 102° West, and
- entire Kitikmeot Region,
-
Saskatchewan
- Lloydminster and surrounding area* (specifically exempted from the legal prohibition of DST in Saskatchewan)
-
Mexico
- Baja California Sur*,
- Chihuahua*,
- Nayarit* (most of state)
- Sinaloa*,
- Sonora
-
United States (MST—Mountain Standard Time)
- Arizona (Navajo Nation does observe DST),
- Colorado*,
-
Idaho*
- south of the Salmon River (between the Oregon state border and the Idaho County/Lemhi County border), and
- east of the Idaho County/Lemhi County border (between the Salmon River and the Montana state border),
- Kansas*
- Montana*,
- Nebraska (western)*,
-
Nevada*
- Duck Valley Indian Reservation, plus the towns of Mountain City and Owyhee,
- Jackpot, and
- West Wendover,
- New Mexico*,
- North Dakota (southwestern)*,
-
Oklahoma
- Kenton*,
-
Oregon
- northern 4/5 of Malheur County*,
- South Dakota (western)*,
-
Texas*
- El Paso County,
- Hudspeth County, and
- northwestern Culberson County,
- Utah*,
- Wyoming*
UTC − 6 S
- Belize
-
Canada (CST—Central Standard Time)
- Manitoba*,
-
Nunavut
- between 85° West and 102° West (except eastern Kitikmeot Region and western Southampton Island)*,
-
Ontario*
- west of 90° West (except Atikokan area, New Osnaburgh and Pickle Lake area, and Shebandowan and Upsala area), and
- Big Trout Lake area east of 90° West,
-
Saskatchewan (most of province), except
- Creighton and Denare Beach area, which does observe DST (unofficially, as Saskatchewan has a law prohibiting the use of DST)
- Chile
- Costa Rica
- Ecuador
- El Salvador
- Guatemala
- Honduras
-
Mexico*
- all other states not already mentioned, plus
- Distrito Federal
-
Nayarit*
- some of Nuevo Vallarta
- Nicaragua
-
United States (CST—Central Standard Time)
- Alabama*,
- Arkansas*,
-
Florida
- west of the Apalachicola River, except for those portions of Franklin County and Gulf County south of the Intracoastal Waterway*,
- Illinois*,
-
Indiana*
- northwestern
- southwestern
- Iowa*,
- Kansas (most of state)*,
- Kentucky (western)*,
- Louisiana*,
- Michigan*
- Minnesota*,
- Mississippi*,
- Missouri*,
- Nebraska (central and eastern)*,
- North Dakota (most of state)*,
- Oklahoma (most of state)*,
- South Dakota (eastern)*,
- Tennessee (central and western)*,
- Texas (most of state)*,
- Wisconsin*
UTC − 5 R
- Bahamas*
- Brazil
- Canada (EST—Eastern Standard Time)
- Cayman Islands
- Colombia
- Cuba*
- Ecuador
- Haiti
- Jamaica
- Panama
- Peru
- Turks and Caicos Islands*
-
United States (EST—Eastern Standard Time)
- Connecticut*,
- Delaware*,
- District of Columbia*,
- Florida (most of state)*,
- Georgia*,
-
Indiana (most of state), except
- Clark County,
- Dearborn County,
- Floyd County,
- Harrison County, and
- Ohio County, which do unofficially observe DST,
- Kentucky (eastern)*,
- Maine*,
- Maryland*,
- Massachusetts*,
- Michigan (most of state)*,
- New Hampshire*,
- New Jersey*,
- New York*,
- North Carolina*,
- Ohio*,
- Pennsylvania*,
- Rhode Island*,
- South Carolina*,
- Tennessee (eastern)*,
- Vermont*,
- Virginia*,
- West Virginia*
UTC − 4 Q
- Anguilla
- Antigua and Barbuda
- Aruba
- Barbados
- Bermuda*
- Bolivia
-
Brazil
- Amazonas (all but southwestern tip),
- Mato Grosso*,
- Mato Grosso do Sul*,
- Pará (western),
- Rondônia,
- Roraima
-
Canada (AST— Atlantic Standard Time)
- Labrador (all but southeastern tip)*,
- New Brunswick*,
- Nova Scotia*,
- Prince Edward Island*,
- Quebec (east of the Natashquan River) (NAO)
- Quebec (east of the 63°W longitude) (CIA)
- Chile*
- Dominica
- Dominican Republic
- Falkland Islands*
-
Greenland - Kalaallit Nunaat
- northwestern
- Pituffik area* (observes United States DST rules)
- northwestern
- Grenada
- Guadeloupe
- Guyana
- Martinique
- Montserrat
- Netherlands Antilles
- Paraguay*
- Puerto Rico (AST—Atlantic Standard Time)
- Saint Kitts and Nevis
- Saint Lucia
- Saint Vincent and the Grenadines
- Trinidad and Tobago
- Venezuela
-
Virgin Islands
- British Virgin Islands and
- U.S. Virgin Islands (AST—Atlantic Standard Time)
UTC − 3:30 P*
-
Canada (NST—Newfoundland Standard Time )
- Labrador (southeastern)*,
- Newfoundland*
UTC − 3 P
- Argentina
- Brazil - official time
- French Guiana
-
Greenland - Kalaallit Nunaat
- south coast and southwest coast* (observes European Union DST rules)
- Saint-Pierre and Miquelon*
- Suriname
- Uruguay*
UTC − 2 O
-
Brazil - Ocean Islands
- Fernando de Noronha, Trindade, Martim Vaz, etc.
- South Georgia and the South Sandwich Islands
UTC − 1 N
- Cape Verde
-
Greenland - Kalaallit Nunaat
- eastern
- Ittoqqortoormiit and surrounding area* (observes European Union DST rules)
- eastern
- Portugal
UTC Z
- Burkina Faso
- Bouvet Island
- Côte d'Ivoire
- Faroe Islands*
- The Gambia
- Ghana
-
Greenland - Kalaallit Nunaat
- northeastern
- Danmarkshavn and surrounding area
- northeastern
- Guinea
- Guinea-Bissau
- Iceland
- Ireland*
- Liberia
- Mali
- Mauritania
- Morocco
- Portugal*
- Saint Helena
- São Tomé and Príncipe
- Senegal
- Sierra Leone
- Spain
- Togo
- United Kingdom* (GMT / BST)
- Western Sahara
UTC + 1 A
- Albania*
- Algeria
- Andorra*
- Angola
- Austria*
- Belgium*
- Benin
- Bosnia and Herzegovina*
- Cameroon
- Central African Republic
- Chad
- Congo, Republic of the
- Congo, Democratic Republic of the (Kinshasa, Bandundu, Bas-Zaire , Equateur )
- Croatia*
- Czech Republic*
- Denmark*
- Equatorial Guinea
- France*
- Gabon
- Germany*
- Gibraltar*
- Hungary*
- Italy*
- Liechtenstein*
- Luxembourg*
- Macedonia, Republic of*
- Malta*
- Monaco*
- Montenegro*
- Namibia*
- Netherlands*
- Niger
- Nigeria
- Norway*
- Poland*
- San Marino*
- Serbia*
- Slovakia*
- Slovenia*
- Spain* (except Canary Islands).
- Svalbard and Jan Mayen*
- Sweden*
- Switzerland*
- Tunisia
- Vatican City*
UTC + 2 B
- Belarus*
- Botswana
- Bulgaria*
- Burundi
- Congo, Democratic Republic of the (Kasai Occidental , Kasai Oriental , Haut-Zaire , Katanga)
- Cyprus*
- Egypt*
- Estonia*
- Finland*
- Gaza Strip*
- Greece*
- Israel*
- Jordan*
- Latvia*
- Lebanon*
- Lesotho
- Libya
- Lithuania*
- Malawi
- Moldova*
- Mozambique
- Romania*
- Russia (Kaliningrad)*
- Rwanda
- South Africa
- Swaziland
- Syria*
- Turkey*
- Ukraine*
- West Bank*
- Zambia
- Zimbabwe
UTC + 3 C
- Bahrain
- Comoros
- Djibouti
- Eritrea
- Ethiopia
- Georgia* ([2] http://news.bbc.co.uk/2/hi/europe/3843511.stm , "same as Moscow", "three hours ahead of London", the text "GMT + 4" in the link apparently refers to the situation in summer)
- Iraq*
- Kenya
- Kuwait
- Madagascar
- Mayotte
- Qatar
- Russia* (most of European portion, including Moscow, St. Petersburg, Rostov on Don, Novaya Zemlya, Franz Josef Land, and all railroads throughout Russia)
- Saudi Arabia
- Somalia
- Sudan
- Tanzania
- Uganda
- Yemen
UTC + 3:30 C*
- Iran*
UTC + 4 D
- Armenia*
- Azerbaijan*
- Kazakhstan (Western)*
- Mauritius
- Oman
- Réunion
- Russia
- Seychelles
- United Arab Emirates
UTC + 4:30 D*
UTC + 5 E
- British Indian Ocean Territory (NAO)
- Heard Island and McDonald Islands
- Kazakhstan (Central)*
- Kyrgyzstan*
- Maldives
- Pakistan
- Russia
- Astrakhan* (CIA)
- Bashkortostan*
- Chelyabinsk*
- Kurgan*
- Orenburg*
- Perm*
- Saratov* (CIA)
- Sverdlovsk* (incl. Yekaterinburg)
- Tyumen*
- Ulyanovsk* (CIA)
- Volgograd* (CIA)
- Tajikistan
- Turkmenistan
- Uzbekistan
UTC + 5:30 E*
- India (IST—Indian Standard Time)
UTC + 5:45 E‡
UTC + 6 F
- Bangladesh
- Bhutan
- British Indian Ocean Territory (CIA)
- Kazakhstan (Eastern)*
- Russia
- Altai Krai*
- Altai Republic*
- Novosibirsk*
- Omsk*
- Tomsk* (NAO),
- Sri Lanka
UTC + 6:30 F*
UTC + 7 G
- Cambodia
- Christmas Island (Australia)
- Indonesia (Western)
- Laos
- Mongolia* (part of western Mongolia)
- Russia
- Kemerovo*
- Khakassia*
- Krasnoyarsk* (incl. Severnaya Zemlya)
- Tomsk* (CIA),
- Tuva*
- Thailand
- Vietnam
UTC + 8 H
-
Australia (AWST—Australian Western Standard Time)
- Western Australia (most of state)
- Brunei
- Mainland China
- Hong Kong (HKT)
- Indonesia (Central)
- Macau
- Malaysia
- Mongolia* (most of country)
- Philippines
- Russia
- Singapore
- Taiwan
Note that the whole of China has the same time, which makes this time zone exceptionally wide. In the extreme west of China the sun is at its highest at 15:00, in the extreme east at 11:00. It also means that on the short (76 km) frontier with Afghanistan, the official time change is 3 hours and 30 minutes.
UTC + 8:45 H‡
-
Australia
-
Western Australia
- Caiguna -Eucla -Border Village (far south-eastern part of state)
-
Western Australia
UTC + 9 I
- East Timor
- Indonesia (Eastern)
- Japan (JST—Japan Standard Time)
- North Korea
- South Korea (KST—Korea Standard Time)
- Palau
- Russia
UTC + 9:30 I*
- Australia (ACST—Australian Central Standard Time)
UTC + 10 K
-
Australia (AEST—Australian Eastern Standard Time)
- Australian Capital Territory*,
- New South Wales* (except Broken Hill, which observes South Australia time),
- Queensland,
- Tasmania*,
- Victoria*
- Guam (Chamorro Standard Time via US Law)
- Federated States of Micronesia
- Northern Mariana Islands (Chamorro Standard Time via US law)
- Papua New Guinea
- Russia
- Primorsky (incl. Vladivostok and Sakhalin Island)*
- Khabarovsk*
- Sakha* (central portion, incl. New Siberian Islands)
UTC + 10:30 K*
-
Australia
-
New South Wales
- Lord Howe Island* (DST only 0:30)
-
New South Wales
UTC + 11 L
UTC + 11:30 L*
UTC + 12 M
- Fiji
- Kiribati
- Marshall Islands
- Nauru
- New Zealand (Aotearoa)*
- Russia
- Chukotka*
- Kamchatka (incl. Kuril Islands)*
- Tuvalu
- Wake Island
- Wallis and Futuna
UTC + 12:45 M‡
UTC + 13 M*
UTC + 14 M†
See also
Bibliography
- Bowditch, Nathaniel. American Practical Navigator. Washington: Government Printing Office, 1925, 1939, 1975.
- Hill, John C., Thomas F. Utegaard, Gerard Riordan. Dutton's Navigation and Piloting. Annapolis: United States Naval Institute, 1958.
- Howse, Derek. Greenwich Time and the Discovery of the Longitude. Oxford: Oxford University Press, 1980. ISBN 0192159488.
External links
- Time Genie http://www.timegenie.com/ Find the current time and date for more than 6,600 cities in 245 countries. Also includes tools for converting and comparing times.
- World Time Server http://www.worldtimeserver.com/
- The E Time zone page http://timezones.tk - Clock, Time and Zones - View the day and night timezone clock around the world at the E Time zone page
- Virtual Travelog http://www.virtualtravelog.net/entries/000031.html A Solution for Managing Time Zones, and Dates in International Internet Systems
- The tz database http://www.twinsun.com/tz/tz-link.htm provides specific information on the beginning and ending dates of daylight saving time for each zone and tracks time zones over the years.