How Many Time Zones Are in the US? 6 for the States, 9 by Law

The United States has six time zones across the 50 states: Eastern, Central, Mountain, Pacific, Alaska and Hawaii-Aleutian. Federal law defines nine in total, adding Atlantic (Puerto Rico and the U.S. Virgin Islands), Samoa (American Samoa) and Chamorro (Guam and the Northern Mariana Islands).

Which number is right depends on what you count:

The nine-zone figure comes straight from statute. 15 U.S.C. § 261 says the territory of the United States "shall be divided into nine zones," and § 263 names them Atlantic, eastern, central, mountain, Pacific, Alaska, Hawaii-Aleutian, Samoa and Chamorro standard time.

You will also see 11 or 12. Those counts add the clock offsets of small uninhabited US islands in the Pacific. Wake Island keeps UTC+12 in the IANA time zone database used by computers, and Baker and Howland Islands are conventionally placed at UTC−12. None of these islands has a zone in the statute, so the legal count stays at nine.

Offsets below are hours from Coordinated Universal Time. The daylight column applies only where daylight saving time is observed (second Sunday in March to first Sunday in November).

The state counts follow the federal boundaries in 49 CFR Part 71, count the District of Columbia separately and include West Wendover, Nevada, in Mountain. Eastern covers the most states, but Central reaches the most states in total, wholly or in part (20).

What those offsets mean at one moment: at noon Eastern Standard Time in January, it is 11:00 a.m. in Chicago, 10:00 a.m. in Denver and Phoenix, 9:00 a.m. in Los Angeles, 8:00 a.m. in Anchorage, 7:00 a.m. in Honolulu and Adak, 1:00 p.m. in San Juan, 6:00 a.m. in Pago Pago and 3:00 a.m. the next day in Guam. That is a spread of 21 hours between American Samoa and Guam, the two ends of US civil time.

The map shows the six zones of the 50 states. It is built from Census county boundaries, with each county colored by the zone that covers most of it, so the zone lines follow county lines the way the federal boundaries mostly do.

Read it as a simplified overview. The boundary files are generalized (1:10 million scale, 2017 edition), a few counties are themselves split between two zones and appear in a single color, and the Aleutians West census area is shown entirely in Hawaii-Aleutian although its eastern islands, including Unalaska, keep Alaska time. The territories are not shown. For a zoomable map with live clocks in each zone, open the US time zone map.

Thirteen states are divided between two zones over a large area, and a fourteenth, Nevada, has a single city on the other side of the line. The table follows the boundary descriptions in 49 CFR §§ 71.5, 71.7, 71.9 and 71.12.

Arizona is often added to such lists, but it sits in one zone. What divides it is daylight saving time: the Navajo Nation changes its clocks and the rest of the state does not. A few border towns also keep the neighboring zone's time informally, such as Phenix City, Alabama (Eastern, with Columbus, Georgia) and Kenton, Oklahoma (Mountain). Those are local customs, not federal boundaries.

If you live or work near one of these lines, What Time Zone Am I In checks your exact position against time zone polygons, which is more reliable than a phone that may be reading a cell tower across the line.

Thirty-six states and the District of Columbia lie in a single zone. Grouped by zone:

The remaining 14 states appear in the split-state table above. Nevada is Pacific except for West Wendover; Alaska is Alaska time except for the far western Aleutians.

Two patterns stand out. First, the Eastern zone holds more states but they are small: the zone line runs down the middle of the Great Lakes states and Appalachia, so populous states such as Indiana, Kentucky, Tennessee and Florida straddle it. Second, the Mountain zone is the least crowded. It covers a wide band of the West, yet Phoenix and Denver are its only metro areas of more than two million people.

For a state-by-state check of a single address, county lines matter more than state lines. What Time Zone Am I In accepts a place name or ZIP code as well as your GPS position and returns the zone and its current offset; the US time zone map snaps a searched place to its zone and shows live clocks for each one.

The number of zones stays the same all year, but the gaps between them do not. Hawaii, most of Arizona and all five territories stay on standard time, so in summer:

• Arizona shows the same clock time as California, and in winter the same as Colorado.
• Hawaii is three hours behind the West Coast in summer and two hours behind in winter.
• Puerto Rico and the U.S. Virgin Islands match the East Coast in summer and run an hour ahead in winter.
• The Aleutian Islands west of 169°30′ W do observe daylight saving time, so Adak and Honolulu match in winter but not in summer.

The same moment, noon in New York, in winter and in summer:

Every row that changes between the two columns is a place that skips daylight saving time while New York observes it.

These rules, and the dates they change, are covered in detail in daylight saving time 2026.

The zones themselves are set by Congress; the lines between them are set by the US Department of Transportation, which writes them into 49 CFR Part 71 and moves them when a county shows that a change serves "the convenience of commerce." That is why the boundaries follow county and state lines and bend around cities instead of running along meridians.

The history, the legal test and how software turns those lines into zone IDs such as America/Chicago are explained in how time zone boundaries work. For any two US places, the time difference calculator gives the gap on a specific date, which accounts for the places that skip daylight saving time.