What is a time zone?

Answer 1

A time zone is a region of the Earth that has adopted the same standard time, usually referred to as the local time. Most adjacent time zones are exactly one hour apart, and by convention compute their local time as an offset from Greenwich Mean Time. Standard time zones can be defined by geometrically subdividing the Earth's spheroid into 24 lunes (wedge-shaped sections), bordered by meridians each 15° of longitude apart. The local time in neighbouring zones is then exactly one hour different. However, political and geographical practicalities can result in irregularly-shaped zones that follow political boundaries or that change their time seasonally (as with daylight saving time), as well as being subject to occasional redefinition as political conditions change.
Any of the 24 longitudinal divisions of the earth's surface in which standard time is kept.

Answer 2

A time zone is one of the 24 time zones around the world. Each time zone is 15 degrees latitude. That classifies that certain locations will have the same time.

E.g Malaysia, Hong Kong, the Philippines, and some other countries share the same time zone of GMT +8 (GMT means Greenwich Mean Time the time of the Prime Meridian which runs through England and Spain).

Local areas will adjust the lines for political and social ease, for instance to keep the entire country in a single time zone. An example is India, which is off by 30 minutes, splitting the difference between what would be the normal two time zones.

Another example is Arizona in the US. They do not observe Daylight Saving Time, so sometimes they are in the Pacific Time Zone and in others they match the Mountain time zone.

Some large countries are divided into several time zones. Take the U.S. for example, it is divided into Eastern, Central, Pacific, and Mountain. That's why it is a four hour time difference from California (Pacific) to Florida (Eastern)

Answer 3

A time zone is an area throughout which the time is the same.

Before time zones started to be established in the 1800s, each city and town kept its own time, with noon being the time, averaged over a whole year, when the sun was at its highest point in the sky as viewed from that city or town. As travel and communication became faster, having a different time in each city and town became more and more confusing.

The Netherlands was the first country to establish a standard time zone when the whole country switched to Amsterdam Mean Time in 1835. Time in the United States was consolidated into four standard time zones, Eastern, Central, Mountain, and Pacific, on the 18th of November 1883.

There are a total of 41 different time zones, or offsets from Coordinated Universal Time (UTC), including UTC itself, in use each year. The total is 40 if you don’t count UTC-12, the time zone of Baker and Howland Islands, which are officially uninhabited. Some time zones, UTC-3:30, UTC-2:30, UTC+3:30, UTC+12:45, and UTC+13:45, are in use during only part of each year due to Daylight Saving Time (a.k.a. Summer Time). That makes the total number of time zones in use in the officially inhabited parts of the world 37 from March to September and 38 from September to March.

Answer 4

There are a total of 41 different time zones, or offsets from Coordinated Universal Time (UTC), including UTC itself, in use each year. The total is 40 if you don’t count UTC-12, the time zone of Baker and Howland Islands, which are officially uninhabited. Some time zones, UTC-3:30, UTC-2:30, UTC+3:30, UTC+12:45, and UTC+13:45, are in use during only part of each year due to Daylight Saving Time (a.k.a. Summer Time). That makes the total number of time zones in use in the officially inhabited parts of the world 37 from March to September and 38 from September to March.

Most time zones each go by several different names. Here is a complete list of time zones with their English language names and abbreviations as of September 2017.

UTC-12

Baker Island Time (BIT)

UTC-11

American Samoa Standard Time (SST)
Niue Time (NUT)

UTC-10

Hawaii-Aleutian Standard Time (HAST)
Cook Islands Time (CKT)
Tahiti Time (TAHT)

UTC-9:30

Marquesas Time (MART)

UTC-9

Hawaii-Aleutian Daylight Saving Time (HADT) — Mar-Nov only
Alaska Standard Time (AKST) — Nov-Mar only
Gambier Time (GAMT)

UTC-8

Alaska Daylight Saving Time (AKDT) — Mar-Nov only
Pacific Standard Time (PST)
Pitcairn Standard Time (PST)

UTC-7

Pacific Daylight Saving Time (PDT) — Mar-Nov only
Mountain Standard Time (MST)

UTC-6

Mountain Daylight Saving Time (MDT) — Mar-Nov only
Central Standard Time (CST)
Galapagos Time (GALT)
Easter Island Time (EAST) — May-Aug only

UTC-5

Central Daylight Saving Time (CDT) — Mar-Nov only
Easter Island Summer Time (EASST) — Aug-May only
Eastern Standard Time (EST)
Cuba Standard Time (CUST) — Nov-Mar only
Colombia Time (COT)
Ecuador Time (ECT)
Peru Time (PET)
Acre Time (ACT)

UTC-4

Eastern Daylight Saving Time (EDT) — Mar-Nov only
Cuba Daylight Saving Time (CUDT) — Mar-Nov only
Atlantic Standard Time (AST)
Venezuelan Standard Time (VET)
Guyana Time (GYT)
Amazon Time (ANT)
Bolivia Time (BOT)
Paraguay Time (PYT) — Mar-Oct only
Chile Time (CLT) — May-Aug only

UTC-3:30

Newfoundland Standard Time (NST) — Nov-Mar only

UTC-3

Atlantic Daylight Saving Time (ADT) — Mar-Nov only
Amazon Summer Time (ANST) — Oct-Feb only
Paraguay Summer Time (PYST) — Oct-Mar only
Chile Summer Time (CLST)
Western Greenland Time (WGT) — Oct-Mar only
Pierre & Miquelon Standard Time (PMST) — Nov-Mar only
Suriname Time (SRT)
French Guiana Time (GFT)
Brasilia Time (BRT)
Argentina Time (ART)
Uruguay Time (UYT)
Falkland Islands Summer Time (FKST)
Rothera Time (ROTT)

UTC-2:30

Newfoundland Daylight Saving Time (NDT) — Mar-Nov only

UTC-2

Western Greenland Summer Time (WGST) — Mar-Oct only
Pierre & Miquelon Daylight Saving Time (PMDT) — Mar-Nov only
Brasilia Summer Time (BRST) — Oct-Feb only
Fernando de Noronha Time (FNT)
South Georgia Time (GST)

UTC-1

Eastern Greenland Time (EGT) — Oct-Mar only
Azores Time (AZOT) — Oct-Mar only
Cape Verde Time (CVT)

UTC+0

Eastern Greenland Summer Time (EGST) — Mar-Oct only
Azores Summer Time (AZOST) — Mar-Oct only
Western European Time (WET) — Oct-Mar only
Greenwich Mean Time (GMT)

UTC+1

Western European Summer Time (WEST) — Mar-Oct only
British Summer Time (BST) — Mar-Oct only
Irish Summer Time (IEST) — Mar-Oct only
Central European Time (CET)
West Africa Time (WAT)

UTC+2

Central European Summer Time (CEST) — Mar-Oct only
West Africa Summer Time (WAST) — Sep-Apr only
Eastern European Time (EET)
Israel Standard Time (ILST) — Oct-Mar only
Central Africa Time (CAT)
South Africa Standard Time (SAST)

UTC+3

Eastern European Summer Time (EEST) — Mar-Oct only
Israel Daylight Saving Time (ILDT) — Mar-Oct only
Moscow Time (MSK)
Belarus Time (BYT)
Arabia Standard Time (AAST)
East Africa Time (EAT)
Syowa Time (SYOT)

UTC+3:30

Iran Standard Time (IRST) — Sep-Mar only

UTC+4

Samara Time (SAMT)
Georgia Time (GET)
Armenia Time (AMT)
Azerbaijan Time (AZT)
Gulf Standard Time (GUST)
Seychelles Time (SCT)
Mauritius Time (MUT)
Réunion Time (RET)

UTC+4:30

Iran Daylight Saving Time (IRDT) — Mar-Sep only
Afghanistan Time (AFT)

UTC+5

Yekaterinburg Time (YEKT)
Aqtau Time (AQTT)
Aqtobe Time (AQTT)
Oral Time (ORAT)
Uzbekistan Time (UZT)
Turkmenistan Time (TMT)
Tajikistan Time (TJT)
Pakistan Time (PKT)
Maldives Time (MVT)
French Southern & Antarctic Time (TFT)
Mawson Time (MAWT)

UTC+5:30

Indian Standard Time (INST)

UTC+5:45

Nepal Time (NPT)

UTC+6

Omsk Time (OMST)
Novosibirsk Time (NOVT)
Almaty Time (ALMT)
Qyzylorda Time (QYZT)
Kyrgyzstan Time (KGT)
Bhutan Time (BTT)
Bangladesh Standard Time (BdST)
Indian Chagos Time (IOT)
Vostok Time (VOST)

UTC+6:30

Myanmar Time (MMT)
Cocos Islands Time (CCT)

UTC+7

Krasnoyarsk Time (KRAT)
Hovd Time (HOVT)
Indochina Time (ICT)
Western Indonesian Time (WIB)
Christmas Island Time (CXT)
Davis Time (DAVT)

UTC+8

Irkutsk Time (IRKT)
Ulaanbaatar Time (ULAT)
Choibalsan Time (CHOT)
China Standard Time (CNST)
Hong Kong Time (HKT)
Philippine Time (PHT)
Brunei Darussalam Time (BNT)
Malaysia Time (MYT)
Singapore Time (SGT)
Central Indonesian Time (WITA)
Australian Western Standard Time (AWST)

UTC+8:30

Pyongyang Time (KPT)

UTC+8:45

Central Western Standard Time (CWST)

UTC+9

Yakutsk Time (YAKT)
South Korea Standard Time (KRT)
Japan Standard Time (JST)
Palau Time (PWT)
Eastern Indonesian Time (WIT)
Timor-Leste Time (TLT)

UTC+9:30

Australian Central Standard Time (ACST)

UTC+10

Vladivostok Time (VLAT)
Sakhalin Time (SAKT)
Magadan Time (MAGT)
Chamorro Standard Time (ChST)
Chuuk Time (CHUT)
Yap Time (YAPT)
Papua New Guinea Time (PGT)
Australian Eastern Standard Time (AEST)
Dumont-d'Urville Time (DDUT)

UTC+10:30

Australian Central Daylight Saving Time (ACDT) — Oct-Apr only
Lord Howe Standard Time (LHST) — Apr-Oct only

UTC+11

Lord Howe Daylight Saving Time (LHDT) — Oct-Apr only
Australian Eastern Daylight Saving Time (AEDT) — Oct-Apr only
Srednekolymsk Time (SRET)
Vanuatu Time (VUT)
New Caledonia Time (NCT)
Solomon Islands Time (SBT)
Norfolk Time (NFT)
Macquarie Island Time (MIST)
Pohnpei Time (PONT)
Kosrae Time (KOST)
Bougainville Standard Time (BOUST)

UTC+12

Anadyr Time (ANAT)
Petropavlovsk-Kamchatski Time (PETT)
Wallis and Futuna Time (WFT)
Fiji Time (FJT) — Jan-Nov only
Tuvalu Time (TVT)
New Zealand Standard Time (NZST) — Apr-Sep only
Gilbert Island Time (GILT)
Marshall Islands Time (MHT)
Nauru Time (NRT)
Wake Time (WAKT)

UTC+12:45

Chatham Island Standard Time (CHAST) — Apr-Sep only

UTC+13

Fiji Summer Time (FJST) — Nov-Jan only
New Zealand Daylight Saving Time (NZDT) — Sep-Apr only
Phoenix Island Time (PHOT)
Tokelau Time (TKT)
Samoa Standard Time (WSST) — Apr-Sep only
Tonga Time (TOT) — Jan-Nov only

UTC+13:45

Chatham Island Daylight Saving Time (CHADT) — Sep-Apr only

UTC+14

Samoa Daylight Saving Time (WSDT) — Sep-Apr only
Tonga Summer Time (TOST) — Nov-Jan only
Line Islands Time (LINT)

Answer 5

Earthly and Planetry