Time Zones

Time zones give specific areas on the Earth a time of day that is earlier or later than the neighboring time zones. This is because when it is day-time on one side of the Earth, it is night-time on the other side. There are 39 time zones dividing the Earth into different times, each with its own name.

Greenwich Mean Time (GMT) is now called UTC (Coordinated Universal Time). All other parts of the world are offset (plus or minus) according to their longitude. Most of the zones are offset by a full hour, but there are some offset by half an hour or 45 minutes.

Time in the United States

Time in the United States is divided into nine standard time zones, with most of the United States observing daylight saving time for approximately the spring, summer, and fall months.

Daylight saving time (DST) or summer time is the practice of advancing clocks during summer months by one hour so that in the evening daylight is experienced an hour longer, while sacrificing normal sunrise times. Typically, regions with summer time adjust clocks forward one hour close to the start of spring and adjust them backward in the autumn to standard time.

The time zone boundaries and DST observance are regulated by the Department of Transportation. Official and highly precise timekeeping services (clocks) are provided by two federal agencies: the National Institute of Standards and Technology (NIST) (an agency of the Department of Commerce); and its military counterpart, the United States Naval Observatory (USNO). The clocks run by these services are kept synchronized with each other as well as with those of other international timekeeping organizations.

USA time zones

United States time zones:

Atlantic Time Zone
Eastern Time Zone
Central Time Zone
Mountain Time Zone
Pacific Time Zone
Alaska Time Zone
Hawaii–Aleutian Time Zone
Samoa Time Zone (UTC-11)
Chamorro Time Zone (UTC+10)

From east to west, the times zones of the contiguous United States are:

Eastern Time Zone: (Zone R), which comprises roughly the states on the Atlantic coast and the eastern two thirds of the Ohio Valley.
Central Time Zone: (Zone S), which comprises roughly the Gulf Coast, Mississippi Valley, and Great Plains.
Mountain Time Zone: (Zone T), which comprises roughly the states that include the Rocky Mountains.
Pacific Time Zone: (Zone U), which comprises roughly the states on the Pacific coast, plus Nevada and the Idaho panhandle.

Zones used in states beyond the contiguous U.S.

Alaska standard time zone: (AKST; UTC-09; Zone V), which comprises most of the state of Alaska.
Hawaii-Aleutian standard time zone: (or unofficially Hawaii Standard Time: HST) (HAST; UTC-10; zone W), which includes Hawaii and most of the length of the Aleutian Islands chain (west of 169°30'W).

Zones outside the states

Atlantic standard time zone: (AST; UTC-04; Zone Q), which comprises Puerto Rico and the U.S. Virgin Islands.
Samoa standard time zone (SST; UTC-11; Zone X), which comprises American Samoa.
Chamorro standard time zone: (ChST; UTC+10; Zone K), which comprises Guam and the Northern Mariana Islands.



WORLD WIDE TIME ZONE ABBREVIATIONS
ABBREVIATION TIME ZONE NAME UTC OFFSET
ACDT AUSTRALIAN CENTRAL DAYLIGHT TIME UTC + 10:30
ACST AUSTRALIAN CENTRAL STANDARD TIME UTC + 9:30
ACWT AUSTRALIAN CENTRAL WESTERN TIME UTC + 8:45
ADT ATLANTIC DAYLIGHT TIME (Caribbean, North America) UTC - 3
ADT ARABIA DAYLIGHT TIME UTC + 3
ACT ACRE TIME (Brazil) UTC - 5
AEDT AUSTRALIAN EASTERN DAYLIGHT TIME UTC + 11
AEST AUSTRALIAN EASTERN STANDARD TIME UTC + 10
AFT AFGHANISTAN TIME UTC + 4:30
AKDT ALASKA DAYLIGHT TIME UTC - 8
AKST ALASKA STANDARD TIME UTC - 9
ALMT ALMA-ATA TIME UTC + 6
AMT ARMENIA TIME UTC + 4
AMT AMAZON TIME UTC - 4
AMST AMAZON SUMMER TIME UTC - 3
AMST ARMENIA SUMMER TIME UTC + 5
ANAT ANADYR TIME (Russia) UTC + 12
ANAST ANADYR SUMMER TIME (Russia) UTC + 12
AQTT AQTOBE TIME (Kazakhstan) UTC + 5
ART ARGENTINA TIME UTC - 3
AST ATLANTIC STANDARD TIME (Caribbean, North America) UTC - 4
AST ARAB STANDARD TIME UTC + 3
AST ARABIA STANDARD TIME UTC + 3
AWDT AUSTRALIAN WESTERN DAYLIGHT TIME UTC + 9
AWST AUSTRALIAN WESTERN STANDARD TIME UTC + 8
AZOT AZORES TIME UTC - 1
AZOST AZORES SUMMER TIME UTC + 0
AZT AZERBAIJAN TIME UTC + 4
AZST AZERBAIJAN SUMMER TIME UTC + 5
BNT BRUNEI TIME UTC + 8
BDT BANGLADESH TIME (also see BST) UTC + 6
BOT BOLIVIA TIME UTC - 4
BRT BRASILIA TIME UTC - 3
BRST BRASILIA SUMMER TIME UTC - 2
BST BRITISH SUMMER TIME UTC + 1
BST BANGLADESH STANDARD TIME (also see BDT) UTC + 6
BTT BHUTAN TIME UTC + 6
CAST CASEY TIME (Antarctica) UTC + 8
CAT CENTRAL AFRICA TIME UTC + 2
CCT COCOS ISLANDS TIME UTC + 6:30
CDT CENTRAL DAYLIGHT TIME (Australia) UTC + 10:30
CDT CENTRAL DAYLIGHT TIME (North America & Caribbean) UTC - 5
CEDT CENTRAL EUROPEAN DAYLIGHT TIME UTC + 2
CEST CENTRAL EUROPEAN SUMMER TIME UTC + 2
CET CENTRAL EUROPEAN TIME (standard time) UTC + 1
CHADT CHATHAM ISLAND DAYLIGHT TIME UTC + 13:45
CHAST CHATHAM ISLAND STANDARD TIME UTC + 12:45
CHOT CHOIBALSAN TIME (Mongolia) UTC + 8
CHOST CHOIBALSAN SUMMER TIME (Mongolia) UTC + 9
CHsT CHAMORRO STANDARD TIME UTC + 10
CHUT CHUUK TIME UTC + 10
CIT CENTRAL INDONESIAN TIME (see abbreviation WITA) UTC + 8
CKT COOK ISLAND TIME UTC - 10
CLST CHILE SUMMER TIME UTC - 3
CLT CHILE STANDARD TIME UTC - 4
COT COLUMBIA TIME UTC - 5
CST CENTRAL STANDARD TIME (Australia) UTC + 9:30
CST CENTRAL STANDARD TIME (North America & Central America) UTC - 6
CST CUBA STANDARD TIME UTC - 5
CST CHINA STANDARD TIME UTC + 8
CVT CAPE VERDE TIME UTC - 1
CWST CENTRAL WESTERN AUSTRALIA TIME (Eucla) UTC + 8:45
CXT CHRISTMAS ISLAND TIME UTC + 7
DAVT DAVIS TIME (Antarctica) UTC + 7
DDUT DUMONT D 'URVILLE TIME UTC + 10
DST DAYLIGHT SAVING TIME VARIES
EASST EASTERN ISLAND SUMMER TIME UTC - 5
EAST EASTERN ISLAND STANDARD TIME UTC - 6
EAT EAST AFRICA TIME UTC + 3
ECT ECUADOR TIME UTC - 5
EDT EASTERN DAYLIGHT TIME (Australia and Pacific) UTC + 11
EDT EASTERN DAYLIGHT TIME (North America and Caribbean) UTC - 4
EEDT EASTERN EUROPEAN DAYLIGHT TIME UTC + 3
EEST EASTERN EUROPEAN SUMMER TIME UTC + 3
EET EASTERN EUROPEAN TIME UTC + 2
EGT EASTERN GREENLAND TIME UTC - 1
EGST EASTERN GREENLAND SUMMER TIME UTC + 0
EST EASTERN STANDARD TIME (Australia and Pacific) UTC + 10
EST EASTERN STANDARD TIME (North America and Caribbean) UTC - 5
EIT EASTERN INDONESIAN TIME (see WIT) UTC + 9
FET FURTHER-EASTERN EUROPEAN TIME UTC + 3
FJT FIJI TIME UTC + 12
FJST FIJI SUMMER TIME UTC + 13
FKST FALKLAND ISLANDS SUMMER TIME UTC - 3
FKT FALKLAND ISLANDS TIME UTC - 4
FNT FERNANDO de NORONHA UTC - 2
GALT GALAPAGOS TIME UTC - 6
GAMT GAMBIER TIME UTC - 9
GET GEORGIA STANDARD TIME UTC + 4
GFT FRENCH GUIANA TIME UTC - 3
GILT GILBERT ISLAND TIME UTC + 12
GMT GREENWICH MEAN TIME UTC + 0
GST GULF STANDARD TIME UTC + 4
GST SOUTH GEORGIA TIME (South Georgia and the South Sandwich Islands) UTC - 2
GYT GUYANA TIME UTC - 4
HADT HAWAII-ALEUTIAN DAYLIGHT TIME UTC - 9
HAST HAWAII-ALEUTIAN STANDARD TIME UTC - 10
HKT HONG KONG TIME UTC + 8
HOVT HOVD TIME (Mongolia) UTC + 7
HOVST HOVD SUMMER TIME (Mongolia) UTC + 8
HST HAWAII STANDARD TIME UTC - 10
ICT INDOCHINA TIME UTC + 7
IDT ISRAEL DAYLIGHT TIME UTC + 3
IOT INDIAN CHAGOS TIME (British Indian Ocean Territory) UTC + 6
IRDT IRAN DAYLIGHT TIME UTC + 4:30
IRKT IRKUTSK TIME UTC + 8
IRKST IRKUTSK SUMMER TIME UTC + 9
IRST IRAN STANDARD TIME UTC + 3:30
IST INDIAN STANDARD TIME UTC + 5:30
IST ISRAEL STANDARD TIME UTC + 2
IST IRISH STANDARD TIME (IST is used during daylight saving time) UTC + 1
JST JAPAN STANDARD TIME UTC + 9
KGT KYRGYZSTAN TIME UTC + 6
KOST KOSRAE TIME (Micronesia) UTC + 11
KRAT KRASNOYARSK TIME UTC + 7
KRAST KRASNOYARSK SUMMER TIME UTC + 8
KST KOREA STANDARD TIME UTC + 9
KUYT KUYBYSHEV TIME (Samara Time as of 1991) UTC + 4
LHDT LORD HOWE DAYLIGHT TIME UTC + 11
LHST LORD HOWE STANDARD TIME UTC + 10:30
LINT LINE ISLANDS TIME UTC + 14
MAGT MAGADAN TIME UTC + 10
MAGST MAGADAN SUMMER TIME UTC + 12
MART MARQUESAS TIME UTC - 9:30
MAWT MAWSON STATION TIME (Antarctic) UTC + 5
MDT MOUNTAIN DAYLIGHT TIME (North America) UTC - 6
MeST METLAKATLA (Alaska Indian Community) UTC - 8
MHT MARSHALL ISLANDS TIME UTC + 12
MIST MACQUARIE ISLAND STATION TIME UTC + 11
MMT MYANMAR TIME UTC + 6:30
MSD MOSCOW SUMMER TIME UTC + 4
MSK MOSCOW STANDARD TIME UTC + 3
MST MOUNTAIN STANDARD TIME (North America) UTC - 7
MUT MAURITIUS TIME UTC + 4
MVT MALDIVES TIME UTC + 5
MYT MALAYSIA TIME UTC + 8
NCT NEW CALEDONIA TIME UTC + 11
NDT NEWFOUNDLAND DAYLIGHT TIME UTC - 2:30
NFT NORFOLK TIME UTC + 11:30
NOVT NOVOSIBIRSK TIME UTC + 6
NOVST NOVOSIBIRSK SUMMER TIME UTC + 7
NPT NEPAL TIME UTC + 5:45
NRT NAURU TIME UTC + 12
NST NEWFOUNDLAND STANDARD TIME UTC - 3:30
NT NEWFOUNDLAND TIME UTC - 3:30
NUT NIUE TIME UTC - 11
NZDT NEW ZEALAND DAYLIGHT TIME UTC + 13
NZST NEW ZEALAND STANDARD TIME UTC + 12
OMST OMSK STANDARD TIME UTC + 6
OMSST OMSK SUMMER TIME UTC + 7
ORAT ORAL TIME UTC + 5
PDT PACIFIC DAYLIGHT TIME (North America) UTC - 7
PET PERU TIME UTC - 5
PETT KAMCHATKA TIME UTC + 12
PETST KAMCHATKA SUMMER TIME UTC + 12
PGT PAPUA NEW GUINEA TIME UTC + 10
PHT PHILIPPINE TIME UTC + 8
PHOT PHOENIX ISLAND TIME UTC + 13
PKT PAKISTAN STANDARD TIME UTC + 5
PMDT PIERRE & MIQUELON DAYLIGHT TIME UTC - 2
PMST PIERRE & MIQUELON STANDARD TIME UTC - 3
PONT POHNPEI TIME (Formerly Ponape) UTC+ 11
PST PACIFIC STANDARD TIME (North America) UTC - 8
PST PITCAIRN TIME UTC - 8
PST PYONGYANG TIME (North Korea) UTC + 8:30
PWT PALAU TIME UTC + 9
PYT PARAGUAY TIME UTC - 4
PYST PARAGUAY SUMMER TIME UTC - 3
QYZT QYZYLORDA TIME (Kazakhstan) UTC +6
RET REUNION TIME UTC + 4
ROTT ROTHERA (RESEARCH STATION) TIME (Antarctica) UTC - 3
SAKT SAKHALIN TIME UTC + 10
SAKST SAKHALIN SUMMER TIME UTC + 12
SAMT SAMARA TIME UTC + 4
SAST SOUTH AFRICA STANDARD TIME UTC + 2
SBT SOLOMON ISLANDS TIME UTC + 11
SCT SEYCHELLES TIME UTC + 4
SGT SINGAPORE TIME UTC + 8
SRT SURINAME TIME UTC - 3
SLT SRI LANKA TIME UTC + 5:30
SLST SRI LANKA TIME UTC + 5:30
SRET SREDNEKOLYMSK TIME UTC + 11
SST SAMOA STANDARD TIME (American Samoa) UTC - 11
SYOT SYOWA (RESEARCH STATION) TIME (Antarctica) UTC + 3
TAHT TAHITI TIME UTC - 10
TFT FRENCH SOUTHERN AND ANTARCTIC TERRITORIES TIME UTC + 5
TJT TAJIKISTAN TIME UTC + 5
TKT TOKELAU TIME UTC + 13
TLT EAST TIMOR TIME (Timor-Leste Time) UTC + 9
TMT TURKMENISTAN TIME UTC + 5
TOT TONGA TIME UTC + 13
TRUT TRUK TIME (Micronesia) UTC + 10
TVT TUVALU TIME UTC + 12
ULAT ULAANBAATAR TIME UTC + 8
ULAST ULAANBAATAR SUMMER TIME UTC + 9
UTC COORDINATED UNIVERSAL TIME UTC + 0
UYST URUGUAY SUMMER TIME UTC - 2
UYT URUGUAY STANDARD TIME UTC - 3
UZT UZBEKISTAN TIME UTC + 5
VET VENEZUELAN STANDARD TIME UTC - 4:30
VLAT VLADIVOSTOK TIME UTC + 10
VLAST VLADIVOSTOK SUMMER TIME UTC + 11
VOLT VOLGOGRAD TIME UTC + 4
VUT VANUATU TIME UTC + 11
WAKT WAKE ISLAND TIME UTC + 12
WAT WEST AFRICA TIME UTC + 1
WART WEST ARGENTINA TIME UTC - 4
WAST WEST AFRICA SUMMER TIME UTC + 2
WDT WESTERN DAYLIGHT TIME (Australia) UTC + 9
WEDT WESTERN EUROPEAN DAYLIGHT TIME UTC + 1
WEST WESTERN EUROPEAN SUMMER TIME UTC + 1
WET WESTERN EUROPEAN TIME UTC + 0
WFT WALLIS AND FUTUNA TIME UTC + 12
WGT WESTERN GREENLAND TIME UTC - 3
WGST WESTERN GREENLAND SUMMER TIME UTC - 2
WIB WESTERN INDONESIAN TIME UTC + 7
WIT EASTERN INDONESIAN TIME UTC + 9
WITA CENTRAL INDONESIAN TIME UTC + 8
WST WESTERN SAHARA SUMMER TIME UTC + 1
WST WESTERN STANDARD TIME (Australia) UTC + 8
WST WESTERN SAMOA TIME (standard time) UTC + 13
WST WESTERN SAMOA TIME (*also used during daylight saving time) UTC + 14
WT WESTERN SAHARA STANDARD TIME UTC + 0
YAKT YAKUTSK TIME UTC + 9
YAKST YAKUTSK SUMMER TIME UTC + 10
YAP YAP TIME (Micronesia) UTC + 10
YEKT YEKATERINBURG TIME UTC + 5
YEKST YEKATERINBURG SUMMER TIME UTC + 6

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