Time zone

Time zones are areas of the Earth that follow the same definition of time. Formerly, people used apparent solar time, resulting in the time differing slightly from town to town. 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 15º; however as the map below shows, the shapes of time zones can be quite irregular because of boundaries of countries.

All time zones are defined relative to Coordinated Universal Time (UTC). The reference point for Time Zones is the Prime Meridian (longitude 000) which passes through the Royal Greenwich Observatory in Greenwich, London, England [1]. 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, as in the rest of Europe, local time is UTC+1 (known in the UK as British Summer Time).

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)
• New York, New York, USA: UTC-5 (e.g. if it is 11:00 UTC, then it is 06:00 in New York)
• 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 after midnight, then the date at the location is one day later. 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)

Where the adjustment for time zones results in a time before 00:00 (i.e. midnight), then the date at the location is one day earlier. Some examples:

• Buenos Aires, Argentina: UTC-4 (e.g. if it is 03:00 UTC on Saturday 23 July, then the time in Buenos Aires is 23:00, Friday 22 July)
• Honolulu, Hawaii, 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!

The military refers to time zones using single letter designations. "Z" is used to denote UTC, time zones ahead of UTC are designated using letters in the first half of the Roman alphabet, and time zones behind UTC are designated using the second half. Time zones with a deviation from UTC of a non-integer quantity of hours use the letter of the nearest whole hour-deviated time zone toward UTC, with a star or dagger added on. The letter "J" refers to local time. There are no jurisdictions that observe the time zone designated by the letter "Y" (UTC-12), but that particular time zone is acknowledged as a point of convenience.

Time zones were invented by Sanford Fleming because of the need of railroad companies to have consistent local times between railroad stations. [1] On 18 November 1883, railroads in the United States and Canada became the first to institute time zones when they established four standard continental time zones in North America. This ended a great deal of confusion created by previously having thousands of local times. Worldwide adoption of time zones followed the next year.

See also: Sidereal time Calculating local time

image:Timezones_small.png
A map of the world's time zones, Larger image

Table of contents

1 List of time zones and contained areas 1.1 UTC-11 (BEST - Bering Standard Time) 1.2 UTC-10 (HST - Hawaii-Aleutian Standard Time) 1.3 UTC-9:30 1.4 UTC-9 (AKST - Alaska Standard Time) 1.5 UTC-8 (PST - Pacific Standard Time) 1.6 UTC-7 (MST - Mountain Standard Time) 1.7 UTC-6 (CST - Central Standard Time) 1.8 UTC-5 (EST - Eastern Standard Time) 1.9 UTC-4 (AST - Atlantic Standard Time) 1.10 UTC-3:30 (NST - Newfoundland Standard Time) 1.11 UTC-3 1.12 UTC-2 1.13 UTC-1 1.14 UTC (WET - West European Time) 1.15 UTC+1 (CET - Central European Time) 1.16 UTC+2 (EET - East European Time) 1.17 UTC+3 (MSK - Moscow Time) 1.18 UTC+3:30 1.19 UTC+4 1.20 UTC+4:30 1.21 UTC+5 1.22 UTC+5:30 (IST - Indian Standard Time) 1.23 UTC+5:45 1.24 UTC+6 1.25 UTC+6:30 1.26 UTC+7 1.27 UTC+8 (AWST - Australian Western Standard Time) 1.28 UTC+9 1.29 UTC+9:30 (ACST - Australian Central Standard Time) 1.30 UTC+10 (AEST - Australian Eastern Standard Time) 1.31 UTC+10:30 1.32 UTC+11 1.33 UTC+11:30 1.34 UTC+12 1.35 UTC+12:45 1.36 UTC+13 1.37 UTC+14 2 External links

List of time zones and contained areas

Regions with * observe Daylight Saving Time: add 1 hour in summer.

Note that some regions differ 24 hours in time: they have the same time of the day but differ by a full day. The two extreme time zones even differ 25 hours, hence during one hour a day the date differs 2 days.

UTC-11 (BEST - Bering Standard Time)

Military designation: X

• American Samoa
• Midway Islands
• Niue
• Samoa

UTC-10 (HST - Hawaii-Aleutian Standard Time)

Military designation: W

• French Polynesia (Society Archipelago including Tahiti, Tuamotu Archipelago, Tubuai Islands)
• Johnston Atoll
• United States (Hawaii)
• United States (Aleutian Islands of Alaska)*

UTC-9:30

Military designation: V*

• French Polynesia (Marquesas Islands)

UTC-9 (AKST - Alaska Standard Time)

Military designation: V

• French Polynesia (Gambier Islands)
• United States (Alaska*)

UTC-8 (PST - Pacific Standard Time)

Military designation: U

• Canada (British Columbia*, Yukon*)
• Mexico (Baja California*)
• United States (California*, Idaho (northern)*, Nevada*, Oregon (except Malheur County)*, Washington*

UTC-7 (MST - Mountain Standard Time)

Military designation: T

• Canada (Alberta*, Northwest Territories*, Nunavut (Mountain)*)
• Mexico (Baja California Sur*, Chihuahua*, Nayarit*, Sinaloa*, Sonora)
• United States (Arizona (Navajo Nation does observe DST), Colorado*, Idaho (southern)*, Montana*, Nebraska (western)*, New Mexico*, North Dakota (western)*, Oregon (Malheur County)* South Dakota (western)*, Utah*, Wyoming*)

UTC-6 (CST - Central Standard Time)

Military designation: S

• Belize
• Canada (Manitoba*, Nunavut (Southampton Island), Nunavut (Central)*, Ontario (Western)*, Saskatchewan)
• Chile (Easter Island)

• Costa Rica
• Ecuador (Galapagos Islands)
• El Salvador
• Guatemala
• Honduras
• Mexico* (all other states not already mentioned, plus Distrito Federal)
• Nicaragua
• United States (Alabama*, Arkansas*, Illinois*, Indiana* (northwest and southwest), Iowa*, Kansas*, Kentucky (western)*, Louisiana*, Minnesota*, Mississippi*, Missouri*, Nebraska (eastern)*, North Dakota*, Oklahoma*, South Dakota (eastern)*, Tennessee (middle and western)*, Texas*, Wisconsin*)

UTC-5 (EST - Eastern Standard Time)

Military designation: R

• Brazil (Acre)
• Canada (Nunavut (Eastern)*, Ontario*, Quebec*)
• Cayman Islands
• Colombia
• Cuba*
• Ecuador
• Haiti
• Jamaica
• Panama
• Peru
• Turks and Caicos Islands*
• United States (Connecticut*, Delaware*, District of Columbia*, Florida*, Georgia*, Indiana (most of state), Kentucky (eastern and central)*, Maine*, Maryland*, Massachusetts*, Michigan*, New Hampshire*, New Jersey*, New York*, North Carolina*, Ohio*, Pennsylvania*, Rhode Island*, South Carolina*, Tennessee (eastern)*, Vermont*, Virginia*, West Virginia*)

UTC-4 (AST - Atlantic Standard Time)

Military designation: Q

• Anguilla
• Antigua and Barbuda
• Aruba
• Barbados
• Bolivia
• Brazil (Amazonas, Mato Grosso*, Mato Grosso do Sul*, Para (western), Rondonia, Roraima)
• Canada (Labrador*, New Brunswick*, Nova Scotia*, Prince Edward Island*)
• Chile*
• Dominica
• Dominican Republic
• Falkland Islands*
• Grenada
• Guadeloupe
• Guyana
• Martinique
• Montserrat
• Netherlands Antilles
• Paraguay*
• Puerto Rico
• Saint Kitts and Nevis
• Saint Lucia
• Saint Vincent and the Grenadines
• Trinidad and Tobago
• Venezuela
• Virgin Islands

UTC-3:30 (NST - Newfoundland Standard Time)

Military designation: P*

• Canada (Newfoundland*)

UTC-3

Military designation: P

• Argentina
• Bahamas*
• Brazil (Alagoas, Amapa, Bahia*, Ceara, Distrito Federal*, Espirito Santo*, Goias*, Maranhao, Minas Gerais*, Para (eastern), Paraiba, Parana*, Pernambuco, Piaui, Rio de Janeiro*, Rio Grande do Norte, Rio Grande do Sul*, Santa Catarina*, Sao Paulo*, Sergipe, Tocantins*)
• French Guiana*
• Greenland
• Saint Pierre and Miquelon*
• Suriname
• Uruguay

UTC-2

Military designation: O

• Bermuda*
• Brazil (Fernando de Noronha)

UTC-1

Military designation: N

• Cape Verde
• Portugal (Azores*)

UTC (WET - West European Time)

Military designation: Z

• Burkina Faso
• Côte d'Ivoire
• Faroe Islands*
• The Gambia
• Ghana
• Guinea
• Guinea-Bissau
• Iceland
• Ireland*
• Liberia
• Mali
• Mauritania
• Morocco
• Portugal*
• Saint Helena
• São Tomé and Príncipe
• Senegal
• Sierra Leone
• Spain* (Canary Islands)
• Togo
• United Kingdom*

UTC+1 (CET - Central European Time)

Military designation: A

• Albania*
• Andorra*
• Angola
• Austria*
• Belgium*
• Benin
• Bosnia and Herzegovina*
• Cameroon
• Central African Republic
• Chad
• Congo, Republic of the
• Congo, Democratic Republic of the (Kinshasa, Bandungu, Bas-Zaire, Equateur)
• Croatia*
• Czech Republic*
• Denmark*
• Equatorial Guinea
• Republic of Macedonia*
• France*
• Gabon
• Germany*
• Gibraltar*
• Hungary*
• Italy*
• Liechtenstein*
• Luxembourg*
• Malta*
• Monaco*
• Montenegro*
• Namibia*
• Netherlands*
• Niger
• Nigeria
• Norway*
• Poland*
• San Marino*
• Serbia*
• Slovakia*
• Slovenia*
• Spain*
• Svalbard and Jan Mayen*
• Sweden*
• Switzerland*
• Tunisia

UTC+2 (EET - East European Time)

Military designation: B

• Belarus*
• Botswana
• Bulgaria*
• Burundi
• Congo, Democratic Republic of the (Kasai Occidental, Kasai Oriental, Haut-Zaire, Shaba)
• Cyprus*
• Egypt*
• Estonia*
• Finland*
• Gaza Strip*
• Greece*
• Israel*
• Jordan
• Latvia*
• Lebanon*
• Lesotho
• Libya
• Lithuania*
• Malawi
• Moldova*
• Mozambique
• Romania*
• Russia (Zone 1*, including Kalingrad)
• Rwanda
• South Africa
• Swaziland
• Syria*
• Turkey*
• Ukraine*
• West Bank*
• Zambia
• Zimbabwe

UTC+3 (MSK - Moscow Time)

Military designation: C

• Bahrain
• Comoros
• Djibouti
• Eritrea
• Ethiopia
• Iraq*
• Kenya
• Kuwait
• Madagascar
• Mayotte
• Qatar
• Russia (Zone 2*, including Moscow and St. Petersburg; this time zone applies also for railways throughout Russia)
• Saudi Arabia
• Somalia
• Sudan
• Tanzania
• Uganda
• Yemen

UTC+3:30

Military designation: C*

• Iran*

UTC+4

Military designation: D

• Georgia*
• Kazakhstan (Western)*
• Mauritius
• Oman
• Reunion
• Russia (Zone 3*)
• Seychelles
• United Arab Emirates

UTC+4:30

Military designation: D*

• Afghanistan

UTC+5

Military designation: E

• Armenia
• Azerbaijan*
• Kazakhstan (Central)*
• Kyrgyzstan*
• Maldives
• Pakistan
• Russia (Zone 4*, including Ekaterinburg and Perm)
• Tajikistan
• Turkmenistan
• Uzbekistan

UTC+5:30 (IST - Indian Standard Time)

Military designation: E*

• India

UTC+5:45

Military designation: E†

• Nepal

UTC+6

Military designation: F

• Bangladesh
• Bhutan
• Kazakhstan (Eastern)*
• Russia (Zone 5*, including Novosibirsk and Omsk)
• Sri Lanka

UTC+6:30

Military designation: F*

• Cocos Islands
• Myanmar

UTC+7

Military designation: G

• Cambodia
• Christmas Island (Australia)
• Indonesia (Western)
• Laos
• Russia (Zone 6*)
• Thailand
• Vietnam

UTC+8 (AWST - Australian Western Standard Time)

Military designation: H

• Australia (Western Australia)
• Brunei
• Mainland China
• Hong Kong
• Indonesia (Central)
• Macau
• Malaysia
• Mongolia
• Philippines
• Russia (Zone 7*)
• 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.

UTC+9

Military designation: I

• East Timor
• Indonesia (Eastern)
• Japan (JST - Japan Standard Time)
• North Korea
• South Korea
• Palau
• Russia (Zone 8*, including Yakutsk)

UTC+9:30 (ACST - Australian Central Standard Time)

Military designation: I*

• Australia (Broken Hill, NSW; Northern Territory; South Australia*)

UTC+10 (AEST - Australian Eastern Standard Time)

Military designation: K
The United States has officially designated this time zone Chamorro Standard Time.

• Australia (Australian Capital Territory*, New South Wales* (except Broken Hill, which observes South Australia time), Queensland, Victoria*, Tasmania*)
• Cook Islands
• Guam
• Federated States of Micronesia (Yap and Chuuk)
• Northern Mariana Islands
• Papua New Guinea
• Russia (Zone 9*, including Vladivostok)

UTC+10:30

Military designation: K*

• Australia (Lord Howe Island*)(DST only 0:30)

UTC+11

Military designation: L

• Federated States of Micronesia (Kosrae and Pohnpei)
• New Caledonia
• Russia (Zone 10*)
• Solomon Islands
• Vanuatu

UTC+11:30

Military designation: L*

• Norfolk Island

UTC+12

Military designation: M

• Fiji*
• Kiribati (Gilbert Islands)
• Marshall Islands
• Nauru
• New Zealand (Aotearoa)*
• Russia (Zone 11*)
• Tuvalu
• Wake Island
• Wallis and Futuna

UTC+12:45

Military designation: M*

• New Zealand (Aotearoa) (Chatham Islands*)

UTC+13

Military designation: M†

• Kiribati (Phoenix Islands)
• Tonga

UTC+14

Military designation: M‡

• Kiribati (Line Islands)

External links

• World Time Server
• A Solution for Managing Time Zones, and Dates in International Internet Systems
• The tz database provides specific information on the beginning and ending dates of daylight saving time for each zone and tracks time zones over the years.