Coordinated Universal Time.

UTC was devised by the International Telecommunication Union (ITU) to mitigate confusion arising from the use of several different time-keeping standards.

The reason it became UTC instead of CUT was that the French abbreviation would have been TUC, so UTC was decided upon as a compromise between the English and French abbreviations. As a result of the re-arrangment, UTC is often usually referred to as Universal Coordinate Time.

Not counting Daylight Saving Time (a.k.a. Summer Time), there are 39 different time offsets used around the world: UTC-11, UTC-10, UTC-9:30, UTC-9, UTC-8, UTC-7, UTC-6, UTC-5, UTC-4:30, UTC-4, UTC-3:30, UTC-3, UTC-2, UTC-1, UTC, UTC+1, UTC+2, UTC+3, UTC+3:30, UTC+4, UTC+4:30, UTC+5, UTC+5:30, UTC+5:45, UTC+6, UTC+6:30, UTC+7, UTC+8, UTC+8:45, UTC+9, UTC+9:30, UTC+10, UTC+10:30, UTC+11, UTC+11:30, UTC+12, UTC+12:45, UTC+13 and UTC+14.

Here are all of the Daylight Saving Time/ Summer Time beginning and ending dates for 2013:

Albania

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Andorra

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Australia

. . . Apr. 7th: UTC+11 --> UTC+10

. . . . . . . . . . .UTC+10.5 --> UTC+9.5

. . . Oct. 6th: UTC+10 --> UTC+11 except Queensland

. . . . . . . . . . .UTC+9.5 --> UTC+10.5 except Northern Territory

Austria

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Azerbaijan

. . . Mar. 31st: UTC+4 --> UTC+5

. . . Oct. 27th: UTC+5 --> UTC+4

Azores (Por.)

. . . Mar. 31st: UTC-1 --> UTC

. . . Oct. 27th: UTC --> UTC-1

Bahamas

. . . Mar. 10th: UTC-5 --> UTC-4

. . . Nov. 3rd: UTC-4 --> UTC-5

Belgium

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Bermuda

. . . Mar. 10th: UTC-4 --> UTC-3

. . . Nov. 3rd: UTC-3 --> UTC-4

Bosnia & Herzegovina

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Brazil

. . . Feb. 17th: UTC-3 --> UTC-4 in Matto Grosso & Matto Grosso do Sul

. . . . . . . . . . . .UTC-2 --> UTC-3 all except Fernando de Noronha

. . . Oct. 20th: UTC-4 --> UTC-3 in Matto Grosso & Matto Grosso do Sul

. . . . . . . . . . . .UTC-3 --> UTC-2 in Tocantins, Espirito Santo, Distrito Federal, Goias, Minas Gerais, Parana, Rio de Janeiro, Rio Grande do Sul, Santa Catarina & São Paulo

Bulgaria

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Canada

. . . Mar. 10th: UTC-3.5 --> UTC-2.5

. . . . . . . . . . . .UTC-4 --> UTC-3 except eastern end of Quebec

. . . . . . . . . . . .UTC-5 --> UTC-4 except Southampton Island & parts of Ontario

. . . . . . . . . . . .UTC-6 --> UTC-5 except Saskatchewan

. . . . . . . . . . . .UTC-7 --> UTC-6 except parts of British Columbia

. . . . . . . . . . . .UTC-8 --> UTC-7

. . . Nov. 3rd: UTC-2.5 --> UTC-3.5

. . . . . . . . . . . UTC-3 --> UTC-4

. . . . . . . . . . . UTC-4 --> UTC-5 except eastern end of Quebec

. . . . . . . . . . . UTC-5 --> UTC-6 except Southampton Island & parts of Ontario

. . . . . . . . . . . UTC-6 --> UTC-7 except Saskatchewan

. . . . . . . . . . . UTC-7 --> UTC-8 except parts of British Columbia

Canary Islands (Sp)

. . . Mar. 31st: UTC --> UTC+1

. . . Oct. 27th: UTC+1 --> UTC

Chatham Island (NZ)

. . . Apr. 7th: UTC+13.75 --> UTC+12.75

. . . Sep. 29th: UTC-12.75 --> UTC+13.75

Chile

. . . Mar. 10th: UTC-3 --> UTC-4

. . . Oct. 13th: UTC-4 --> UTC-3

Croatia

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Cuba

. . . Mar. 10th: UTC-5 --> UTC-4

. . . Nov. 3rd: UTC-4 --> UTC-5

Cyprus

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Czech Republic

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Denmark

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Easter Island (Chile)

. . . Mar. 10th: UTC-5 --> UTC-6

. . . Oct. 13th: UTC-6 --> UTC-5

Estonia

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Fiji:

. . . Jan. 20th: UTC+13 --> UTC+12

. . . Oct. 20th: UTC+12 --> UTC+13

Finland

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

France

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Germany

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Gibraltar (UK)

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Greece

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Greenland (Den.)

. . . Mar. 31st: UTC --> UTC+1

. . . . . . . . . . . .UTC-1 --> UTC

. . . . . . . . . . . .UTC-3 --> UTC-2

. . . Oct. 27th: UTC+1 --> UTC

. . . . . . . . . . . UTC --> UTC-1

. . . . . . . . . . . UTC-2 --> UTC-3

. . . (The Thule area follows the same schedule as Bermuda.)

Hungary

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Iran

. . . Mar. 22nd: UTC+3.5 --> UTC+4.5

. . . Sep. 22nd: UTC+4.5 --> UTC+3.5

Ireland

. . . Mar. 31st: UTC --> UTC+1

. . . Oct. 27th: UTC+1 --> UTC

Israel

. . . Mar. 29th: UTC+2 --> UTC+3

. . . Oct. 6th: UTC+3 --> UTC+2

Italy

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Jordan

. . . Oct. 25th: UTC+3 --> UTC+2

Kosovo

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Latvia

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Lebanon

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Libya

. . . Mar. 29th: UTC+1 --> UTC+2

. . . Oct. 25th: UTC+2 --> UTC+1

Liechtenstein

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Lithuania

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Lord Howe Island (Aus.)

. . . Apr. 7th: UTC+11 --> UTC+10.5

. . . Oct. 6th: UTC+10.5 --> UTC+11

Luxembourg

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Macedonia

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Madeira Islands (Por.)

. . . Mar. 31st: UTC --> UTC+1

. . . Oct. 27th: UTC+1 --> UTC

Malta

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Mexico

. . . Apr. 7th: UTC-6 --> UTC-5

. . . . . . . . . . .UTC-7 --> UTC-6 except Sonora

. . . . . . . . . . .UTC-8 --> UTC-7

. . . Oct. 27th: UTC-5 --> UTC-6

. . . . . . . . . . . UTC-6 --> UTC-7

. . . . . . . . . . . UTC-7 --> UTC-8 except Sonora

. . . (Note: Acuna, Anahuac, Ciudad Juarez, Metamoros, Mexicali, Nuevo Laredo, Ojinaga, Piedras Negras, Reynosa y Tijuana follow the U.S. schedule.)

Moldova

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Monaco

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Montenegro

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Morocco

. . . Apr. 28th: UTC --> UTC+1

. . . Jul. 9th: UTC+1 --> UTC

. . . Aug. 8th: UTC --> UTC+1

. . . Sep. 29th: UTC+1 --> UTC

Namibia

. . . Apr. 7th: UTC+2 --> UTC+1

. . . Sep. 1st: UTC+1 --> UTC+2

Netherlands

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

New Zealand

. . . Apr. 7th: UTC+13 --> UTC+12

. . . Sep. 29th: UTC+12 --> UTC+13

Norway

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Paraguay

. . . Apr. 14th: UTC-3 --> UTC-4

. . . Oct. 6th: UTC-4 --> UTC-3

Poland

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Portugal

. . . Mar. 31st: UTC --> UTC+1

. . . Oct. 27th: UTC+1 --> UTC

Romania

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Saint-Pierre & Miquelon Islands (Fr)

. . . Mar. 10th: UTC-3 --> UTC-2

. . . Nov. 3rd: UTC-2 --> UTC-3

Samoa

. . . Apr. 7th: UTC+14 --> UTC+13

. . . Sep. 29th: UTC+13 --> UTC+14

San Marino

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Serbia

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Slovakia

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Slovenia

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Spain

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Sweden

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Switzerland

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

Syria

. . . Mar. 29th: UTC+2 --> UTC+3

. . . Oct. 25th: UTC+3 --> UTC+2

Turkey

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

Turks & Caicos Islands

. . . Mar. 10th: UTC-5 --> UTC-4

. . . Nov. 3rd: UTC-4 --> UTC-5

Ukraine

. . . Mar. 31st: UTC+2 --> UTC+3

. . . Oct. 27th: UTC+3 --> UTC+2

United Kingdom

. . . Mar. 31st: UTC --> UTC+1

. . . Oct. 27th: UTC+1 --> UTC

United States

. . . Mar. 10th: UTC-5 --> UTC-4

. . . . . . . . . . . .UTC-6 --> UTC-5

. . . . . . . . . . . .UTC-7 --> UTC-6 except most of Arizona

. . . . . . . . . . . .UTC-8 --> UTC-7 except Metlakatla AK

. . . . . . . . . . . .UTC-9 --> UTC-8

. . . . . . . . . . . .UTC-10 --> UTC-9 Aleutian Islands only

. . . Nov. 3rd: UTC-4 --> UTC-5 except Puerto Rico & the Virgin Islands

. . . . . . . . . . . UTC-5 --> UTC-6

. . . . . . . . . . . UTC-6 --> UTC-7

. . . . . . . . . . . UTC-7 --> UTC-8 except Arizona

. . . . . . . . . . . UTC-8 --> UTC-9 except Metlakatla AK

. . . . . . . . . . . UTC-9 --> UTC-10

Uruguay

. . . Mar. 10th: UTC-2 --> UTC-3

. . . Oct. 6th: UTC-3 --> UTC-2

Vatican City

. . . Mar. 31st: UTC+1 --> UTC+2

. . . Oct. 27th: UTC+2 --> UTC+1

UTC - 12 hrs.,

UTC - 11 hrs.,

UTC - 10 hrs.,

UTC - 9.5 hrs.,

UTC - 9 hrs.,

UTC - 8 hrs.,

UTC - 7 hrs.,

UTC - 6 hrs.,

UTC - 5 hrs.,

UTC - 4.5 hrs.,

UTC - 4 hrs.,

either UTC - 3.5 hrs. or UTC - 2.5 hrs.,

UTC - 3 hrs.,

UTC - 2 hrs.,

UTC - 1 hr.,

UTC,

UTC + 1 hr.,

UTC + 2 hrs.,

UTC + 3 hrs.,

sometimes UTC + 3.5 hrs.,

UTC + 4 hrs.,

UTC + 4.5 hrs.,

UTC + 5 hrs.,

UTC + 5.5 hrs.,

UTC + 5.75 hrs.,

UTC + 6 hrs.,

UTC + 6.5 hrs.,

UTC + 7 hrs.,

UTC + 8 hrs.,

UTC + 8.75 hrs.,

UTC + 9 hrs.,

UTC + 9.5 hrs.,

UTC + 10 hrs.,

UTC + 10.5 hrs.,

UTC + 11 hrs.,

UTC + 11.5 hrs.,

UTC + 12 hrs.,

either UTC + 12.75 hrs. or UTC + 13.75 hrs.,

UTC + 13 hrs. and

UTC + 14 hrs.