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What are the US Time Zones?

Dan Cavallari
Dan Cavallari

Officially, there are nine US time zones spanning the contiguous United States, the non-contiguous United States, and territories of the United States. The four US time zones within the contiguous United States are, from east to west, the Eastern Time Zone, Central Time Zone, Mountain Time Zone, and the Pacific Time Zone. The Alaska Time Zone includes the U.S. state of Alaska, and the Hawaii-Aleutian Time Zone includes the U.S. state of Hawaii and the Aleutian Islands.

The Eastern Time Zone is the easternmost of all US time zones, and it runs from the Atlantic Coast westward through most of the Ohio Valley. The Central Time Zone runs from the border of the eastern standard time zone westward through the great plains. The mountain standard time zone runs the length of the Rocky Mountains and the states that contain them, and the Pacific Time Zone includes Pacific coastal states as well as the state of Nevada.

A global map, including time zone divisions.
A global map, including time zone divisions.

The US time zones do not necessarily stop at state borders. For example, South Dakota is divided nearly down the middle between the central standard time zone and the mountain standard time zone. North Dakota's southwest corner is also divided between the two. Indiana is divided between two US time zones, and therefore only part of the state observed daylight saving time, but since 2005, the entire state uses standard time and observes daylight savings time.

When it is 8 a.m. in New York in the Eastern Time Zone, it is 5 a.m. in Los Angeles in the Pacific Time Zone.
When it is 8 a.m. in New York in the Eastern Time Zone, it is 5 a.m. in Los Angeles in the Pacific Time Zone.

As one moves westward through the US time zones, the clock falls back one hour for each time zone. For example, if one passes from the Eastern Time Zone to the Central Time Zone, the time will change at the border from two o'clock p.m. to one o'clock p.m. However, because some sections of the country -- the Hopi Nation in Arizona, for example -- do not observe daylight savings time, this rule does not always hold true.

Discussion Comments

Melonlity

That's not been done in the United States and we don't want it done. China operates under one time zone and it's a mess. By all rights, there should be five time zones in China, but using one means that days and nights don't exactly fall where they should in many parts of the country.

Markerrag

There may be technically nine time zones in the United States, but most of us are only worried about four -- Eastern, Central, Mountain and Pacific. Television networks have worked out ways to deal with those so they are the most convenient for viewers, but people living in Alaska and Hawaii are kind of out of luck in that regard.

Has there ever been an attempt to put the entire country under one, unified time zone?

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    • A global map, including time zone divisions.
      By: Ruslan Olinchuk
      A global map, including time zone divisions.
    • When it is 8 a.m. in New York in the Eastern Time Zone, it is 5 a.m. in Los Angeles in the Pacific Time Zone.
      By: dimedrol68
      When it is 8 a.m. in New York in the Eastern Time Zone, it is 5 a.m. in Los Angeles in the Pacific Time Zone.
    • All of Alaska except the Aleutian Islands is in the Alaska Time Zone.
      By: juan35mm
      All of Alaska except the Aleutian Islands is in the Alaska Time Zone.