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:

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

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:

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