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 New Dehli)
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!

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.

A map of the world's time zones,

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
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)

UTC-4 (AST - Atlantic Standard Time)

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

Canada (Newfoundland*)

UTC-3

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

UTC-1

Cape Verde
Portugal (Azores*)

UTC (WET - West European Time)

UTC+1 (CET - Central European Time)

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)

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)

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

Iran*

UTC+4

UTC+4:30

Afghanistan

UTC+5

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

UTC+5:30

India

UTC+5:45

Nepal

UTC+6

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

UTC+6:30

UTC+7

UTC+8 (AWST - Australian Western Standard Time)

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.