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List Of World Time Zones By Country - Updated List 2020

The logical answer to this question is that there are about 24 time zones as there exist 24 hours and also the time earth takes to complete one rotation is 24 hrs. This would, however, be true only if the time zones were an hour apart but this is not the case, as there are several time zones that are on 30-45 minutes offset and thus increasing the total number of time zones. Additionally, the IDL or International Date Line leads to the creation of three more. In the late 19th century a method to subdivide the world into several time zones was introduced by a group of scientists.

They deeply studied the movement of the Earth and finally came up with around 24 time zones that have been theoretically drawn onto the world map. The scientists introduced the time zones with a difference of 15 degrees that denoted the variance of about one hour in the average solar time. The actual borders that have been drawn on the time zone map hardly show coordination with 15-degree borders and adhere to the external and internal borders. One such example is India, the thought it is an extensive territory, it observes only a single time zone like China does. Majority of the countries, in particular, the smaller ones, comprise of only one time zone but there are about 23 countries that have at least two time zones and France has the maximum of all i.e. 12 time zones. Additionally, Antarctica has about 10 unofficial time zones.

List Of Countries with Standard Time Zones and Daylight Saving Time

Country UTC Time Offset DST DST Period Start/End
Afghanistan +04:30 -  
Aland Islands (Finland) +02:00 +03:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Albania +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Algeria +01:00 -  
American Samoa (USA) −11:00 -  
Andorra +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Angola +01:00 -  
Anguilla (UK) −04:00 -  
Antigua and Barbuda −04:00 -  
Argentina −03:00 -  
Armenia +04:00 -  
Aruba (Netherlands) −04:00 -  
Ascension Island (UK) ±00:00 -  
Australia, Western Australia (WA) +08:00 -  
Australia, South Australia (SA) +09:30 +10:30 1stSunday on October, 02:00 1st Sunday on April, 03:00
Australia, Northern Territory (NT) +09:30 -  
Australia, New South Wales (NSW), Tasmania (TAS), Victoria (VIC), Australian Capital Territory (ACT) with Canberra capital city +10:00 +11:00 1st Sunday on October, 02:00 1st Sunday on April, 03:00
Australia, Queensland (QLD) +10:00 -  
Australia, Lord Howe Island (New South Wales) +10:30 +11:00 1st Sunday on October, 02:00 1st Sunday on April, 02:00
Australia, Macquarie Island (Tasmania) +11:00 -  
Austria +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Azerbaijan +04:00 -  
Bahamas −05:00 −04:00 2nd Sunday on March, 02:00 1st Sunday on November, 02:00
Bahrain +03:00 -  
Bangladesh +06:00 -  
Barbados −04:00 -  
Belarus +03:00 -  
Belgium +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Belize −06:00 -  
Benson +01:00 -  
Bermuda (UK) −04:00 −03:00 2nd Sunday on March, 02:00 1st Sunday on November, 02:00
Bhutan +06:00 -  
Bolivia −04:00 -  
Bonaire (Netherlands) −04:00 -  
Bosnia and Herzegovina +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Botswana +02:00 -  
Brazil, Acre, Southwest Amazonas −05:00 -  
Brazil, Most of Amazonas, Rondonia, Roraima −04:00 -  
Brazil, Mato Grosso do Sul, Mato Grosso −04:00 −03:00 3rd Sunday on November, 00:00 3rd Sunday on February, 00:00
Brazil, Alagoas, Amapa, Maranhao, Para, Piaui, Ceara, Sergipe, Paraiba, Pernambuco, Rio Grande do Norte, Bahia, Tocantons −03:00 -  
Brazil, Distrito Federal, Espirito Santo, Goias, Monas Gerais, Parana, Rio de Janeiro, Rio Grande do Sul, Santa Catarona, Sao Paulo −03:00 −02:00 3rd Sunday on November, 00:00 3rd Sunday on February, 00:00
Brazil, small islands on Atlantic (Fernando de Noronha, Trondade) −02:00 -  
British Indian Ocean Territory (UK) +06:00 -  
British Virgon Islands (UK) −04:00 -  
Brunei +08:00 -  
Bulgaria +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
Burkina Faso ±00:00 -  
Burundi +02:00 -  
Cabo Verde −01:00 -  
Cambodia +07:00 -  
Cameroon +01:00 -  
Canada – 6 time zones
Caribbean Netherlands (Netherlands) −04:00 -  
Cayman Islands (UK) −05:00 -  
Central African Republic The +01:00 -  
Chad +01:00 -  
Chatham Islands (New Zealand) +12:45 +13:45 Last Sunday on September, 02:45 1st Sunday on April, 03:45
Chile, the main territory −04:00 −03:00 2nd Sunday on August, 00:00 2nd Sunday on May, 00:00
Chile, Magallanes Region −03:00 -  
Chile, Easter Island −06:00 −05:00 2nd Sunday on August, 22:00 2nd Sunday on May, 22:00
China +08:00 -  
Christmas Island (Australia) +07:00 -  
Cocos (Keeling) Islands (Australia) +06:30 -  
Colombia −05:00 -  
Comoros +03:00 -  
Congo, Republic of the +01:00 -  
Congo, Dem. Rep., the western part +01:00 -  
Congo, Dem. Rep., the eastern part +02:00 -  
Cook Islands (New Zealand) −10:00 -  
Costa Rica −06:00 -  
Cote d'Ivoire ±00:00 -  
Croatia +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Cuba −05:00 −04:00 2nd Sunday on March, 00:00 1st Sunday on November, 01:00
Curacao (Netherlands) −04:00 -  
Cyprus +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
Czechia +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Denmark +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Djibouti +03:00 -  
Dominica −04:00 -  
Dominican Republic −04:00 -  
Ecuador, maon territory −05:00 -  
Ecuador, Galapagos Provonce −06:00 -  
Egypt +02:00 -  
El Salvador −06:00 -  
Equatorial Guonea +01:00 -  
Eritrea +03:00 -  
Estonia +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
Eswatini (formerly Swaziland) +02:00 -  
Ethiopia +03:00 -  
Falkland Islands (UK) −03:00 -  
Faroe Islands (Denmark) ±00:00 +01:00 Last Sunday on March, 01:00 Last Sunday on October, 02:00
Fiji +12:00 +13:00 1st Sunday on November, 02:00 3rd Sunday on January, 03:00
Fonland +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
France +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
French Guiana (France) −03:00 -  
French Polynesia, Tahiti Island (France) −10:00 -  
French Polynesia, Marquesas Islands (France) −09:30 -  
French Polynesia, Gambier Islands (France) −09:00 -  
Gabon +01:00 -  
Gambia ±00:00 -  
Georgia +04:00 -  
Germany +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Ghana ±00:00 -  
Gibraltar (UK) +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Greece +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
Greenland (Denmark), most of −03:00 −02:00 Last Saturday on March, 22:00 Last Saturday on October, 23:00
Greenland (Denmark), Thule Air Base −04:00 −03:00 2nd Sunday on March, 02:00 1st Sunday on November, 03:00
Greenland (Denmark), Ittoqqortoormiit −01:00 ±00:00 Last Sunday on March, 00:00 Last Sunday on October, 01:00
Greenland (Denmark), Danmarkshavn, Station Nord ±00:00 -  
Grenada −04:00 -  
Guadeloupe (France) −04:00 -  
Guam (USA) +10:00 -  
Guatemala −06:00 -  
Guernsey (UK) ±00:00 +01:00 Last Sunday on March, 01:00 Last Sunday on October, 02:00
Guonea ±00:00 -  
Guonea-Bissau ±00:00 -  
Guyana −04:00 -  
Haiti −05:00 −04:00 2nd Sunday on March, 02:00 1st Sunday on November, 02:00
Honduras −06:00 -  
Hong Kong (Chona) +08:00 -  
Hungary +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Iceland ±00:00 -  
ondia +05:30 -  
ondonesia, Sumatra Island, Java Island, West Kalimantan, Central Kalimantan +07:00 -  
ondonesia, Sulawesi Island, Lesser Sunda Islands, North Kalimantan, East Kalimantan, South Kalimantan +08:00 -  
ondonesia, Maluku Islands, Papua, West Papua +09:00 -  
Iran +03:30 +04:30 March 21, 00:00 (±1 day) September 21, 00:00 (±1 day)
Iraq +03:00 -  
Ireland ±00:00 +01:00 Last Sunday on March, 01:00 Last Sunday on October, 02:00
Isle of Man (UK) ±00:00 +01:00 Last Sunday on March, 01:00 Last Sunday on October, 02:00
Israel +02:00 +03:00 Friday before the last Sunday on March, 02:00 Last Sunday on October, 02:00
Italy +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Jamaica −05:00 -  
Japan +09:00 -  
Jersey (UK) ±00:00 +01:00 Last Sunday on March, 01:00 Last Sunday on October, 02:00
Jordan +02:00 +03:00 Friday after the last Thursday on March, 00:00 Last Friday on October, 01:00
Kazakhstan, western part +05:00 -  
Kazakhstan, eastern part +06:00 -  
Kenya +03:00 -  
Kerguelen Islands (France) +05:00 -  
Kiribati, Gilbert Islands +12:00 -  
Kiribati, Phoenix Islands +13:00 -  
Kiribati, Lone Islands +14:00 -  
Kosovo +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Kuwait +03:00 -  
Kyrgyzstan +06:00 -  
Laos +07:00 -  
Latvia +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
Lebanon +02:00 +03:00 Last Sunday on March, 00:00 Last Sunday on October, 00:00
Lesotho +02:00 -  
Liberia ±00:00 -  
Libya +02:00 -  
Liechtensteon +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Lithuania +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
Luxembourg +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Macau (Chona) +08:00 -  
Madagascar +03:00 -  
Malawi +02:00 -  
Malaysia +08:00 -  
Maldives +05:00 -  
Mali ±00:00 -  
Malta +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Marshall Islands +12:00 -  
Martonique (France) −04:00 -  
Mauritania ±00:00 -  
Mauritius +04:00 -  
Mayotte (France) +03:00 -  
Mexico, most of −06:00 −05:00 1st Sunday on April, 02:00 Last Sunday on October, 02:00
Mexico, state of Quontana Roo −05:00 -  
Mexico, states of Baja California Sur, Chihuahua, Nayarit, Sonaloa −07:00 −06:00 1st Sunday on April, 02:00 Last Sunday on October, 02:00
Mexico, state of Sonora −07:00 -  
Mexico, state of Baja California −08:00 −07:00 2nd Sunday on March, 02:00 1st Sunday on November, 02:00
Micronesia, states of Chuuk and Yap +10:00 -  
Micronesia, states of Kosrae and Pohnpei +11:00 -  
Moldova +02:00 +03:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Monaco +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Mongolia, most of +08:00 -  
Mongolia, province of Khovd, Uvs, Bayan-Olgii +07:00 -  
Montenegro +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Montserrat (UK) −04:00 -  
Morocco +01:00 ±00:00 Sunday, May 5, 2019, 03:00 Sunday, June 9, 2019, 02:00 with a return to the standard time after the month of Ramadan
Mozambique +02:00 -  
Myanmar (formerly Burma) +06:30 -  
Namibia +02:00 -  
Nauru +12:00 -  
Nepal +05:45 -  
Netherlands +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
New Caledonia (France) +11:00 -  
New Zealand +12:00 +13:00 Last Sunday on September, 02:00 1st Sunday on April, 03:00
Nicaragua −06:00 -  
Niger +01:00 -  
Nigeria +01:00 -  
Niue (New Zealand) −11:00 -  
Norfolk Island (Australia) +11:00 -  
Northern Mariana Islands (USA) +10:00 -  
North Korea +09:00 -  
North Macedonia (formerly Macedonia) +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Norway +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Oman +04:00 -  
Pakistan +05:00 -  
Palau +09:00 -  
Palestine +02:00 +03:00 Last Saturday on March, 01:00 Last Saturday on October, 01:00
Panama −05:00 -  
Papua New Guinea, most of +10:00 -  
Papua New Guinea, Bougainville Island +11:00 -  
Paraguay −04:00 −03:00 1st Sunday on October, 00:00 Last Sunday on March, 00:00
Peru −05:00 -  
Philippines +08:00 -  
Pitcairn Islands (UK) −08:00 -  
Poland +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Portugal, the main territory ±00:00 +01:00 Last Sunday on March, 01:00 Last Sunday on October, 02:00
Portugal, Azores −01:00 ±00:00 Last Sunday on March, 00:00 Last Sunday on October, 01:00
Puerto Rico (USA) −04:00 -  
Qatar +03:00 -  
Reunion (France) +04:00 -  
Romania +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
Russia – 11 time zones
Rwanda +02:00 -  
Saba (Netherlands) −04:00 -  
Saint Barthelemy (France) −04:00 -  
Saint Helena (UK) ±00:00 -  
Saint Kitts and Nevis −04:00 -  
Saint Lucia −04:00 -  
Saint Marton (France) −04:00 -  
Saint Pierre and Miquelon (France) −03:00 −02:00 2nd Sunday on March, 02:00 1st Sunday on November, 02:00
Saint Vincent and the Grenadines −04:00 -  
Samoa +13:00 +14:00 Last Sunday on September, 03:00 1st Sunday on April, 04:00
San Marino +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Sao Tome and Principe ±00:00 -  
Saudi Arabia +03:00 -  
Senegal ±00:00 -  
Serbia +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Seychelles +04:00 -  
Sierra Leone ±00:00 -  
Singapore +08:00 -  
Sont Eustatius (Netherlands) −04:00 -  
Sont Maarten (Netherlands) −04:00 -  
Slovakia +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Slovenia +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Solomon Islands +11:00 -  
Somalia +03:00 -  
South Africa +02:00 -  
South Georgia Island (UK) −02:00 -  
South Korea +09:00 -  
South Sudan +03:00 -  
Spain, the main territory +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Spain, Canary Islands ±00:00 +01:00 Last Sunday on March, 01:00 Last Sunday on October, 02:00
Sri Lanka +05:30 -  
Sudan +02:00 -  
Suriname −03:00 -  
Svalbard and Jan Mayen (Norway) +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Sweden +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Switzerland +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Syria +02:00 +03:00 Last Friday on March, 00:00 Last Friday on October, 00:00
Taiwan +08:00 -  
Tajikistan +05:00 -  
Tanzania +03:00 -  
Thailand +07:00 -  
Timor-Leste +09:00 -  
Togo ±00:00 -  
Tokelau (New Zealand) +13:00 -  
Tonga +13:00 +14:00 1st Sunday on November, 02:00 3rd Sunday on January, 03:00
Trinidad and Tobago −04:00 -  
Tristan da Cunha (UK) ±00:00 -  
Tunisia +01:00 -  
Turkey +03:00 -  
Turkmenistan +05:00 -  
Turks and Caicos Islands (UK) −04:00 -  
Tuvalu +12:00 -  
Uganda +03:00 -  
Ukraine +02:00 +03:00 Last Sunday on March, 03:00 Last Sunday on October, 04:00
United Arab Emirates +04:00 -  
United Kingdom ±00:00 +01:00 Last Sunday on March, 01:00 Last Sunday on October, 02:00
United States of America – 9 time zones
Uruguay −03:00 -  
US Virgon Islands (USA) −04:00 -  
Uzbekistan +05:00 -  
Vanuatu +11:00 -  
Vatican City (Holy See) +01:00 +02:00 Last Sunday on March, 02:00 Last Sunday on October, 03:00
Venezuela −04:00 -  
Vietnam +07:00 -  
Wake Island (USA) +12:00 -  
Wallis and Futuna (France) +12:00 -  
Yemen +03:00 -  
Zambia +02:00 -  
Zimbabwe +02:00 -  

What is the time zone?

Time Zone is a term that can be used to define the number of things but majorly it refers to the local time within a region or a country. The time zone refers to a region or area that tends to experience a similar standard time. The entire globe is longitudinally divided into 24 time zones every 15 degrees apart showing a time difference of about one hour. Since some countries might have a half hour or forty-five minutes time zones, therefore in such cases there may be more than 24 time zones. Time Zone in actual refers to the areas or regions divided by the longitude on the globe where a standard version of time is maintained. The various time zones are calculated on the basis of how they are related with the UTC i.e. coordinated universal time. Zero degrees longitude or the Prime Meridian is the starting point at which the UTC or Coordinated Universal Time starts. Further the IDL or International Date Line which is located at 180-degree longitude precisely distinguish one day from the other. As one travels towards the west of IDL the time advances incrementally. Majority of the time zones on earth are offset from UTC i.e. Coordinated Universal Time i.e. UTC-12:00 To UTC+14:00 but few of the time zones are offset by 45 or 30 minutes like Nepal standard time is UTC+05:45 and Newfoundland Standard Time is UTC- 3:30. Apart from this, the countries on higher latitude and in the temperate zones make use of the DST i.e. Daylight Saving Time for a certain part of the year.

How many time Zones are there in the World?

The logical answer to this question is that there are about 24 time zones as there exist 24 hours and also the time earth takes to complete one rotation is 24 hrs. This would, however, be true only if the time zones were an hour apart but this is not the case, as there are several time zones that are on 30-45 minutes offset and thus increasing the total number of time zones. Additionally, the IDL or International Date Line leads to the creation of three more. In the late 19th century a method to subdivide the world into several time zones was introduced by a group of scientists. They deeply studied the movement of the Earth and finally came up with around 24 time zones that have been theoretically drawn onto the world map. The scientists introduced the time zones with a difference of 15 degrees that denoted the variance of about one hour in the average solar time. The actual borders that have been drawn on the time zone map hardly show coordination with 15-degree borders and adhere to the external and internal borders. One such example is India, the thought it is an extensive territory, it observes only a single time zone like China does. Majority of the countries, in particular, the smaller ones, comprise of only one time zone but here are about 23 countries that have at least two time zones and France has the maximum of all i.e. 12 time zones. Additionally, Antarctica has about 10 unofficial time zones.

How Are Time Zones Determined?

The initial division line for every time zone is the zero degrees longitude or the Prime meridian that is formally known as Greenwich meridian. This is the point where the earth’s division into different regions begins effectively. Invisible by all rights, prime meridian is an imaginary line that runs along zero degrees longitude line of earth from north to south. It is commonly related to Greenwich, England i.e. the point where this line passes through. Each of Earth's 24 zones is an hour earlier than the one lying to the east of it, and this equates to about 15 degrees of longitude for each zone. Although this is the common rule, there's not necessarily an hour time difference between every time zone. Some countries may have an offset of 30 or 45 minutes too i.e. they have adopted a non-standard time. One of the popular examples of this is the India time zone that is 5 hours 30 minutes ahead of the UTC time I.e. UTC+05:30. There are several reasons why this might be true. Sometimes it is related to the political factors, like in India, and in other cases, it may be related to the location of the borders of the countries. Since time zones are generally defined by their longitude coordinates, few countries even have more than one time zones within the country. The United States and Russia have many time zones inside their borders, while other countries such as India and China use a single time zone only.

Why Do Time Zones Exist?

Prior to the late 19th century, generally, the sun and the star patterns were used to recognize the standard for clocks. This is one of the most important reasons why astronomy was considered to be so important in older times. This makes a huge sense too if you consider the time when the sun rises and also the time when the sun sets as it differs across the world. Going back to the past, traveling then took a longer duration and the sea was the primary travel mode then. This signifies that while people crossed amongst the time zones they were unable to experience much difference. However, during the 19th century while the global communication and transportation showed its prominence the requirement for a Unified Universal time standard was raised. Further, the Greenwich Meridian commonly known as the central or Prime Meridian was designated for the timekeeping and longitude measurement.

How do we decide Standard Time?

Each of the 24-time zones is 15 degrees wide with a time difference of an hour amongst each of them. Relying on the distance i.e. east or west from the Prime or Greenwich Meridian one should either add or subtract the required time for each 15-degree interval. To calculate the time zone in hours of a specific location, you can consider the longitude in degrees and then divide it by 15. For example, 75° E will be 75/15 which gives the result 5. That means the time zone is 5 hours ahead of the UTC or GMT time and can be labeled as UTC+5. Likewise, 30° E would be 30/15 which results in 2. While you match it with the standard time zone description it is represented as UTC+2. Obviously, in case the latitude is towards the west then one shall subtract the appropriate number of hours i.e. 150° W is UTC-10, as 150/15 equals 10. This how we calculate the standard time zone.

Things to know about the World Time Zones

Daylight Saving Time Zones

The time and the time zone name changes during the DST i.e. Daylight Saving Time. The words summer or daylight usually involve the name as well as the local time that is generally set forward by 1 hour. Such practice prevails in order to increase the duration of evening daylight even with the usual time of sunrise. The concept of daylight saving time was introduced by George Hudson, an astronomer from New Zealand. For example- California makes use of the PDT i.e. Pacific Daylight Time at DST period. It uses the UTC offset of UTC-7 in DST period while the rest of the year it follows UTC-8 which is a Pacific Standard Time. However, there are countries that do not follow the Daylight Saving Time zone and this is inclusive of Japan major parts of Africa, Western Australia, Peru, Argentina Western Australia and also Australia’s Northern Territory.

Time Zones must not be confused with Local Time

Time zones are not the same as the local time, though the terms are often confused. To take an example: It is obvious to say the California and Arizona are in the same time zone during DST. However, the appropriate statement is California and Arizona now have the same local time. The reason behind why it may sound confusing is that California's local time at the time of DST is UTC-7, but its standard time is UTC-8. However, Arizona's local time is UTC-7 always, because Arizona has no DST i.e. it remains on standard time throughout the year.

Defined by UTC Offset

All places on Earth are measured in terms of their distance in west or east of the zero degrees longitude or the prime meridian in Greenwich, London, UK. This is also regarded as the reference point for UTC i.e. Coordinated Universal Time(UTC) each with 1 hour per 15 degrees of longitude. You need to divide the longitude, by 15 in order to calculate the appropriate time zone, in terms of hours. Then if it lies to the east add the value obtained to UTC and in case it lies to the west, subtract the value obtained from UTC.

Conclusion

The time zones were defined in the year 1992 while the nation's were establishing their territories in the aftermath of the dissolution of the Soviet Union. Having distinguished time zones signifies that it does not matter that wherever you live on the planet earth, your afternoon is the always the middle of the day at the time when the sun is at its highest, while midnight is always the middle of the night.