How Many Time Zones Are There In The United States?
The United States does not use a single American time zone. The contiguous 48 states have four primary zones—Eastern, Central, Mountain, and Pacific. Counting Alaska and Hawaii brings the total to six. With populated overseas territories included, the map of time zones covers nine federally recognized offsets. For technical, maritime, and military use that also includes remote uninhabited atolls under U.S. jurisdiction, the count rises to 11.
| Zone Group |
Count |
Included Regions & Boundaries |
| Contiguous Mainland |
4 |
Eastern, Central, Mountain, Pacific Standard Zones |
| Non-Contiguous States |
2 |
Alaska Time, Hawaii-Aleutian Time |
| Populated Territories |
3 |
Atlantic (PR/VI), Chamorro (Guam/MP), Samoa Standard Time (AS) |
| Uninhabited Atolls |
2 |
Wake Island Time (UTC+12), Anywhere on Earth (UTC-12) |
Daylight Saving Time (DST): Most of the U.S. observes DST, with a few exceptions noted below. Clocks spring forward one hour on the second Sunday in March and fall back one hour on the first Sunday in November. During DST, abbreviations use "D" (for example, EDT or PDT). The rest of the year is Standard Time, marked with "S" (for example, EST or PST).
Who Sets U.S. Time Zones?
Time zone boundaries in the United States are set by the U.S. Department of Transportation (DOT), not by astronomy agencies. Standard time zones date back to November 18, 1883, when the railroads adopted them to make train schedules safer and more consistent. Changes today are handled under Title 15 of the U.S. Code.
U.S. Time Zones and IANA IDs
Below are the U.S. zones on our timezone map, with their IANA identifiers and the areas they cover.
Eastern Time (IANA ID: America/New_York, America/Detroit)
Standard (EST): UTC-5 | Daylight (EDT): UTC-4
Covers much of the East Coast, including New York, Washington, D.C., Florida, Pennsylvania, Massachusetts, Georgia, and the eastern parts of Michigan, Kentucky, and Tennessee.
Central Time (IANA ID: America/Chicago, America/Indiana/Knox)
Standard (CST): UTC-6 | Daylight (CDT): UTC-5
Covers the Midwest and Gulf Coast, including Illinois, most of Texas (except the El Paso area), Minnesota, Iowa, Missouri, Oklahoma, Arkansas, Louisiana, and the western parts of Tennessee and Kentucky.
Mountain Time (IANA ID: America/Denver, America/Boise)
Standard (MST): UTC-7 | Daylight (MDT): UTC-6
Covers the Rockies, including Colorado, Utah, Montana, Wyoming, New Mexico, southern Idaho, and western North Dakota and South Dakota.
Arizona (Mountain Time, no DST) (IANA ID: America/Phoenix)
Year-round UTC-7 — Arizona does not observe daylight saving time.
Exception: the Navajo Nation in northeastern Arizona (America/Shiprock) does observe DST and shifts to UTC-6 in summer, so it stays aligned with Navajo lands in Utah and New Mexico. The Hopi Reservation, which sits inside Navajo land, stays on year-round UTC-7 like the rest of Arizona.
Pacific Time (IANA ID: America/Los_Angeles)
Standard (PST): UTC-8 | Daylight (PDT): UTC-7
Covers California, Washington, most of Oregon (except Malheur County), Nevada, and northern Idaho.
Alaska Time (IANA ID: America/Anchorage, America/Nome)
Standard (AKST): UTC-9 | Daylight (AKDT): UTC-8
Covers most of Alaska, including Anchorage, Fairbanks, and Juneau.
Hawaii-Aleutian Time (IANA ID: Pacific/Honolulu, America/Adak)
Hawaii (Pacific/Honolulu): HST (UTC-10) year-round — no DST.
Aleutian Islands (America/Adak): HAST (UTC-10) in winter and HADT (UTC-9) in summer.
U.S. Territories (No DST)
Puerto Rico & U.S. Virgin Islands (America/Puerto_Rico): AST (Atlantic Standard Time, UTC-4) year-round.
Guam & Northern Mariana Islands (Pacific/Guam, Pacific/Saipan): ChST (Chamorro Standard Time, UTC+10) year-round.
American Samoa (Pacific/Pago_Pago): SST (Samoa Standard Time, UTC-11) year-round.
When U.S. Clocks Change for DST
Under the Energy Policy Act, most of the country changes clocks on these dates:
- Spring forward: On the second Sunday in March, at 2:00 a.m. local standard time, clocks jump ahead to 3:00 a.m. That day is only 23 hours long.
- Fall back: On the first Sunday in November, at 2:00 a.m. local daylight time, clocks go back to 1:00 a.m. That hour repeats, so the day is 25 hours long.
Why Doesn’t Most of Arizona Use Daylight Saving Time?
Most of Arizona stays on Mountain Standard Time (UTC-7) year-round and does not spring forward. The main reason is practical: summers in Arizona are already extremely hot, and shifting clocks ahead would push daylight later into the evening, when temperatures are still high and cooling demand is at its peak. Arizona is allowed to sit out DST under the Uniform Time Act, as long as it remains on standard time.
One local exception: the Navajo Nation in northeastern Arizona does observe DST, so it stays in sync with Navajo lands in Utah and New Mexico. The Hopi Reservation, surrounded by Navajo land, stays on year-round MST like the rest of Arizona.
East Coast to West Coast Time Difference
Across the continental United States, the East Coast and West Coast are three hours apart year-round. When it is 9:00 a.m. Eastern, it is 6:00 a.m. Pacific. For meetings that need both coasts, 1:00 p.m. to 5:00 p.m. Eastern (10:00 a.m. to 2:00 p.m. Pacific) is usually the easiest overlap.
For cities outside the U.S., try our World Meeting Planner to find overlapping hours, or our Time Zone Converter to convert a specific time.
Where This Page’s Time Data Comes From
The clocks and zone labels on this page follow the IANA Time Zone Database. For a broader overview of U.S. time zones, see Time in the United States (opens in new tab).
