Washington, D.C. sits in Eastern Time. On a January afternoon it runs five hours behind London and two ahead of São Paulo. Come July, those gaps shrink by an hour because the clocks have sprung forward. The United States doesn't stop at one zone, or four, or even six. It stretches across nine official federal time zones when you count the inhabited territories.
The Short Answer: 9 Official Federal Time Zones
Federal law recognises nine time zones across US soil. The Department of Transportation oversees the boundaries and daylight saving observance under 15 USC §260-267. The table below lays out all nine.
| Time Zone | UTC Offset (Standard) | UTC Offset (DST) | Areas Covered |
|---|---|---|---|
| Eastern Time (ET) | UTC−5 | UTC−4 | Eastern US, including New York, Washington DC, Atlanta |
| Central Time (CT) | UTC−6 | UTC−5 | Great Lakes to Gulf Coast: Chicago, Dallas, New Orleans |
| Mountain Time (MT) | UTC−7 | UTC−6 | Rocky Mountain states: Denver, Salt Lake City, Phoenix (no DST) |
| Pacific Time (PT) | UTC−8 | UTC−7 | West Coast: Los Angeles, San Francisco, Seattle |
| Alaska Time (AKT) | UTC−9 | UTC−8 | Most of Alaska (except western Aleutians) |
| Hawaii-Aleutian Time (HST) | UTC−10 | UTC−9 (Hawaii stays UTC−10) | Hawaii, western Aleutian chain |
| Atlantic Time (AST) | UTC−4 | None | Puerto Rico, US Virgin Islands |
| Samoa Time (SST) | UTC−11 | None | American Samoa |
| Chamorro Time (ChST) | UTC+10 | None | Guam, Northern Mariana Islands |
The Six State Zones
The contiguous United States runs on four zones. Alaska and Hawaii add two more, making six that cover the 50 states.
Eastern Time (ET)
Eastern Time (UTC−5 in winter, UTC−4 in summer) holds the largest population of any US zone. Washington, D.C. sits here. On the March equinox the city sees sunrise at 07:13 and sunset at 19:19, packing 12 hours 6 minutes of light. By the June solstice that stretches to 14 hours 54 minutes, with the sun up at 05:42 and down at 20:36. The December solstice shrinks it to 9 hours 26 minutes. New York and Atlanta share the zone.
Central Time (CT)
Central Time (UTC−6 in winter, UTC−5 in summer) sweeps from the Great Lakes to the Gulf Coast. Chicago, Dallas, and New Orleans all run on it. When it's noon in Washington on winter time, it's 11:00 in Chicago.
Mountain Time (MT)
Mountain Time (UTC−7 in winter, UTC−6 in summer) covers the Rockies. Denver and Salt Lake City sit here. Arizona does not observe DST and stays on Mountain Standard Time year-round. Phoenix therefore matches Pacific Daylight Time every summer.
Pacific Time (PT)
Pacific Time (UTC−8 in winter, UTC−7 in summer) runs the West Coast. Los Angeles, San Francisco, Seattle. Three hours behind Washington, always.
Alaska Time (AKT)
Alaska Time (UTC−9 in winter, UTC−8 in summer) covers most of the state. The western Aleutian chain uses Hawaii-Aleutian Time instead. Alaska once juggled four zones; it consolidated to two in 1983.
Hawaii-Aleutian Time (HST)
Hawaii stays on UTC−10 year-round. The Aleutian chain west of 169°30′W uses the same zone but springs forward to UTC−9 during DST. Hawaii hasn't touched a clock since 1967.
Atlantic Standard Time (AST): Puerto Rico and US Virgin Islands
Atlantic Standard Time (UTC−4) applies in Puerto Rico and the US Virgin Islands. No DST, so the offset never budges. When Washington is on Eastern Standard Time (UTC−5), San Juan runs an hour ahead. When Washington shifts to Eastern Daylight Time (UTC−4), the two match.
Chamorro Standard Time (ChST): Guam and Northern Mariana Islands
Chamorro Time (UTC+10) serves Guam and the Northern Mariana Islands in the western Pacific. These territories are among the first US soil to greet a new day. DST is not observed.
Samoa Standard Time (SST): American Samoa
American Samoa runs on UTC−11. It sits just east of the International Date Line, making it one of the last inhabited places to end any given calendar day. No DST.
Minor Outlying Islands
Wake Island uses UTC+12. Midway Atoll runs on UTC−11, same as American Samoa. Baker Island and Howland Island sit even further off the grid. These specks of land are uninhabited, so they carry no official civilian time zone and fall outside the nine-zone federal count.
Why 9 and Not 6? Territories Count
The six state zones appear on most classroom maps. The three territory zones exist because US jurisdiction reaches the Caribbean and the Pacific. Without Atlantic, Samoa, and Chamorro, official timekeeping would ignore millions of residents in Puerto Rico, Guam, the US Virgin Islands, American Samoa, and the Northern Mariana Islands.
How the 9 Zones Stack Up Globally
Russia leads with 11 zones. France, counting its overseas departments and territories, claims 12. China runs one zone (UTC+8) across a landmass wider than the contiguous US. Nine puts the United States among the most time-diverse nations.
Daylight Saving Time Across the Zones
Most of the US springs forward on the second Sunday in March and falls back on the first Sunday in November. Clocks move at 02:00 local time. The switch ripples simultaneously: when Eastern hits 02:00, it's 01:00 Central, 00:00 Mountain, and 23:00 the previous day in Pacific.
Exceptions:
- Hawaii stays on its usual time. It was exempted from the Uniform Time Act in 1967.
- Arizona (except the Navajo Nation) stays on Mountain Standard Time. The state opted out in 1968 to avoid stretching brutal summer heat into the evening. The Hopi Reservation, inside the Navajo Nation, also skips DST, creating a DST doughnut.
- Puerto Rico, US Virgin Islands, Guam, Northern Mariana Islands, and American Samoa do not observe DST.