Time Zones of the United States
|Basic time zone concepts|
Mercer County, ND switched from Mountain time to Central time in November, 2010.
Daylight Saving Time runs from the second Sunday in March at 02:00 until the first Sunday in November at 02:00 in all zones.
|Area||Standard||DST||Std Abbrev||DST Abbrev||Zone Name|
|Mountain Time (no DST)||UTC-7||MST||America/Phoenix|
|Hawaii-Aleutian Time (no DST)||UTC-10||HST||Pacific/Honolulu|
Use this table to find out what zone a specific location is in.
|Alaska||America/Anchorage||All except Aleutians|
|America/Adak||Aleutian Islands west of 169°W., and Saint Lawrence Island|
|Arizona||America/Phoenix||All except Navajo reservation|
|America/Denver||Navajo reservation in Arizona, excluding Hopi partitioned lands|
|District of Columbia||America/New_York|
|Florida||America/New_York||All except the counties mentioned below|
|America/Chicago||Bay, Calhoun, Escambia, Holmes, Jackson, Okaloosa, Santa Rosa, Walton, and Washington counties and northern Gulf county (panhandle)|
|Idaho||America/Denver||All except the counties mentioned below|
|America/Los_Angeles||Benewah, Bonner, Boundary, Clearwater, Kootenai, Latah, Lewis, Nez Perce, and Shoshone counties and Idaho county north of the Salmon River (panhandle)|
|Indiana||America/New_York||All except the counties mentioned below|
|America/Chicago||Gibson, Jasper, Lake, La Porte, Newton, Perry, Porter, Posey, Spencer, Starke, Vanderburgh, and Warrick counties|
|Kansas||America/Chicago||All except the counties mentioned below|
|America/Denver||Greeley, Hamilton, Sherman, and Wallace counties (in west)|
|Kentucky||America/New_York||All except the counties mentioned below|
|America/Chicago||Adair, Allen, Ballard, Barren, Breckinridge, Butler, Caldwell, Calloway, Carlisle, Christian, Clinton, Crittenden, Cumberland, Daviess, Edmonson, Fulton, Graves, Grayson, Green, Hancock, Hart, Henderson, Hickman, Hopkins, Livingston, Logan, Lyon, Marshall, McCracken, McLean, Metcalfe, Monroe, Muhlenberg, Ohio, Russell, Simpson, Todd, Trigg, Union, Warren, and Webster counties (western Kentucky)|
|Michigan||America/New_York||All except the counties mentioned below|
|America/Chicago||Dickinson, Gogebic, Iron, and Menominee counties (part of upper peninsula)|
|Nebraska||America/Chicago||All except the counties mentioned below|
|America/Denver||Arthur, Banner, Box Butte, Chase, Cheyenne, Dawes, Deuel, Dundy, Garden, Grant, Hooker, Keith, Kimball, Morrill, Perkins, Scotts Bluff, Sheridan, and Sioux counties and the western part of Cherry county (western Nebraska)|
|Nevada||America/Los_Angeles||All of the state except West Wendover|
|America/Denver||West Wendover (city)|
|North Dakota||America/Chicago||All except the counties mentioned below|
|America/Denver||Adams, Billings, Bowman, Golden Valley, Grant, Hettinger, Slope, and Stark counties, the southern parts of Dunn and McKenzie counties, and Sioux county west of ND route 31 (southwestern North Dakota)|
|Oregon||America/Los_Angeles||All except the county mentioned below|
|America/Denver||Malheur county (excluding a small strip in the south)|
|South Dakota||America/Chicago||All except the counties mentioned below|
|America/Denver||Bennett, Butte, Corson, Custer, Dewey, Fall River, Haakon, Harding, Jackson, Lawrence, Meade, Pennington, Perkins, Shannon, and Ziebach counties, and the western part of Stanley county (western South Dakota)|
|Tennessee||America/Chicago||All except the counties mentioned below|
|America/New_York||Anderson, Blount, Bradley, Campbell, Carter, Claiborne, Cocke, Grainger, Greene, Hamblen, Hamilton, Hancock, Hawkins, Jefferson, Johnson, Knox, Loudon, McMinn, Meigs, Monroe, Morgan, Polk, Rhea, Roane, Scott, Sevier, Sullivan, Unicoi, Union, and Washington counties (eastern Tennessee)|
|Texas||America/Chicago||All except the counties mentioned below|
|America/Denver||El Paso and Hudspeth counties and the northwest corner of Culberson county (west Texas)|
I derived the following information by comparing time zone maps from different years. Using this procedure, I can only estimate the dates of changes. The maps themselves seem inconsistent, and in some cases may be showing de facto rather than de jure time zones.
The names Eastern, Central, Mountain, and Pacific have been used for the four time zones of the 48 contiguous states since the beginning of standard time in the United States. Alaska used to have four time zones: Pacific, Yukon, Alaska, and Bering. As of October 30, 1983, this was changed to the two existing time zones, Alaska and Hawaii-Aleutian.
"Eastern Time" can be used to designate the local time at any point in the Eastern zone. "Eastern Standard Time" is used only when standard time is in effect at the given location; "Eastern Daylight Time", only when DST is in effect. The same pattern is followed in all of the U.S. time zones.
Currently, the U.S. system of time zone names also encompasses "Samoa Time" (used in American Samoa), "Chamorro Time" (Guam and Northern Mariana Islands), and "Atlantic Time" (Puerto Rico and U.S. Virgin Islands). All of these zones are standard only, no DST. "ChST" is being proposed as an abbreviation for Chamorro Standard Time, but there is no approved way of abbreviating Atlantic Standard Time to distinguish it from Alaska Standard Time.
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