US time zones

The nine time zones of the United States on a map, with the time now in each, the states in each, and the corners of the country that do not change their clocks.

How to use it

  1. Click anywhere on the map for the zone at that point and the time there.
  2. Read the table of every US zone with the time now.
  3. Read the colours by the offset in force now.

5 practical uses

  1. Schedule a call or a webinar across the US.
  2. Check the time zone of a city, a county or an address.
  3. Know where the clocks do not change in summer.
  4. Plan a road trip through zone changes.
  5. Set the time zone of a device or a server for a US location.

The maths behind it

The map is a raster over the US bounding box: for each pixel the latitude comes from the inverse Mercator formula, the IANA zone from a compressed quadtree of the zone boundaries, and the colour from the zone's current UTC offset. The times in the table are the browser's time zone database applied to the present moment.

The zones

The contiguous states use four zones, Eastern (UTC−5), Central (−6), Mountain (−7) and Pacific (−8), each an hour later in summer. Alaska is on Alaska time (−9) apart from the western Aleutians on Hawaii-Aleutian time (−10); Hawaii is also −10 but does not observe daylight saving, and neither does Arizona outside the Navajo Nation, so in summer Arizona matches California. Puerto Rico and the Virgin Islands use Atlantic time (−4) all year; Guam and the Northern Marianas are on Chamorro time (+10), and American Samoa on Samoa time (−11), so the country spans 21 hours.

Zone lines follow county lines in most places, drawn by the Department of Transportation; thirteen states straddle two zones. The map uses the IANA time zone database, evaluated in the browser.

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Questions and answers

Which states have two time zones?

Thirteen: Alaska, Florida, Idaho, Indiana, Kansas, Kentucky, Michigan, Nebraska, North Dakota, Oregon, South Dakota, Tennessee and Texas.

Which places do not change their clocks?

Hawaii, most of Arizona, Puerto Rico, the US Virgin Islands, Guam, the Northern Marianas and American Samoa.

Who draws the zone lines?

The Department of Transportation, mostly along county lines.

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