Time Zones of the USA

Like all time zones worldwide, the time zones for the USA are based on UTC (Coordinated Universal Time, formerly GMT, Greenwich Mean Time – originally based on London, UK).

The United States observes 9 time zones as below:

• four time zones in the contiguous USA
• two time zones beyond the contiguous USA
• three time zones in US territories

The time zone on the east coast is called Eastern Time (ET), divided into:

• Eastern Standard Time (EST), which is used during autumn/winter and is five hours behind UTC
• Eastern Daylight Time (EDT), which is used during spring/summer and is four hours behind UTC

Other US time zones follow the same format; and moving westward, each time zone adds an additional 1-hour offset.

The 4 time zones of the contiguous USA and the 2 timezones (Alaska, Hawaii) beyond the contiguous USA. (Public Domain)

Time zones in the contiguous USA

zone
and abbreviations*

Standard Time offset from UTC
Daylight Saving Time offset from UTC
states
Eastern
ET, EST, EDT
UTC -5:00
UTC -4:00
Connecticut, Delaware, District of Columbia, Georgia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Vermont, Virginia, West Virginia;
Partially: Florida, Indiana, Kentucky, Michigan, Tennessee

Central
CT, CST, CDT
UTC -6:00
UTC -5:00
Alabama, Arkansas, Illinois, Iowa, Louisiana, Minnesota, Mississippi, Missouri, Oklahoma, Wisconsin;
Partially: Florida, Indiana, Kansas, Kentucky, Michigan, Nebraska, North Dakota, South Dakota, Tennessee, Texas

Mountain
MT, MST, MDT
UTC -7:00
UTC -6:00
Arizona, Colorado, Montana, New Mexico, Utah, Wyoming;
Partially: Idaho, Kansas, Nebraska, North Dakota, Oregon, South Dakota, Texas

Pacific
PT, PST, PDT
UTC -8:00
UTC -7:00
California, Nevada, Washington (state);
Partially: Idaho, Oregon

Spring Forward, Fall Back
This mnemonic reminds us that in the spring the clocks move forwards and in the autumn (also called “fall” in US English) they move backwards.

Time zones in states beyond the contiguous USA

zone and abbreviations*
Standard Time offset from UTC
Daylight Saving Time offset from UTC
states
Alaska
AKT, AKST, AKDT
UTC -9:00
UTC -8:00
Partially: Alaska

Hawaii
HT, HST, HDT
UTC -10:00
UTC -9:00
California, Nevada, Washington (state); Partially: Idaho, Oregon

Time zones in US territories

In addition to the six time zones above, the USA observes three time zones in US territories:

• Samoa Time Zone (UTC -11:00) comprising American Samoa in the Pacific
• Chamorro Time Zone (UTC +10:00) comprising Guam and the Norther Mariana Islands in the western Pacific
• Atlantic Time Zone (UTC -4:00) comprising Puerto Rico and the US Virgin Islands in the Caribbean

contiguous (adjective): joined together, touching, adjacent

GMT (abbreviation): Greenwich Mean Time is the standard time in the UK based on the London borough of Greenwich

UTC (abbreviation): Universal Time Coordinated or Coordinated Universal Time, effectively a successor to GMT

*Time zone abbreviations

ET
Eastern Time

EST
Eastern Standard Time

EDT
Eastern Daylight Time

CT
Central Time

CST
Central Standard Time

CDT
Central Daylight Time

MT
Mountain Time

MST
Mountain Standard Time

MDT
Mountain Daylight Time

PT
Pacific Time

PST
Pacific Standard Time

PDT
Pacific Daylight Time

AKT
Alaska Time

AKST
Alaska Standard Time

AKDT
Alaska Daylight Time

HT
Hawaii Time

HST
Hawaii Standard Time

HDT
Hawaii Daylight Time