How many time zones are there in the United States?
The United States does not use a single national clock. This page shows 11 live zone clocks that cover the places most people need day to day:
| Shown on this page |
Count |
Zones |
| Mainland (with Arizona split out) |
5 |
Eastern, Central, Mountain (DST areas), Arizona (no DST), Pacific |
| Alaska & Hawaii chain |
3 |
Alaska, Aleutian (Adak), Hawaii |
| Populated territories |
3 |
Atlantic (Puerto Rico / U.S. Virgin Islands), Chamorro (Guam / Northern Mariana Islands), Samoa (American Samoa) |
| Total live clocks |
11 |
The clocks above this FAQ |
Other U.S. jurisdictions exist for technical or maritime use—for example Wake Island (UTC+12) and Baker / Howland Island (UTC−12)—but this page does not show live clocks for those uninhabited areas. The mainland graphic is a static map image that illustrates the four primary contiguous zones; it is not an interactive or county-level boundary tool.
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 represented by the live clocks on this page, with their common IANA identifiers and the areas they cover. These IDs are listed here for reference; they are not labeled on the static map image.
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 (UTC-4) year-round.
Guam & Northern Mariana Islands (Pacific/Guam, Pacific/Saipan): ChST (UTC+10) year-round.
American Samoa (Pacific/Pago_Pago): SST (UTC-11) year-round.
See U.S. territories time zones below for scheduling notes versus the mainland.
When do 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.
How does Indiana split Eastern and Central time?
Indiana is not a single-offset state. Most counties—including Indianapolis, Fort Wayne, Bloomington, and South Bend—use Eastern Time (America/Indiana/Indianapolis and related IANA zones) and observe the same March / November DST change as New York. A minority of counties sit on Central Time: several in the northwest near Chicago (for example Lake, Porter, LaPorte, Newton, and Jasper) and a cluster in the southwest near Evansville (for example Gibson, Posey, Vanderburgh, Warrick, and Spencer). Those Central counties are commonly represented with IANA IDs such as America/Chicago, America/Indiana/Knox, or America/Indiana/Tell_City, depending on the locality.
The practical trap is treating “Indiana” as Eastern by default. A 9:00 a.m. meeting in Chicago (Central) is 10:00 a.m. in Indianapolis (Eastern) year-round under current rules, because both sides observe DST on the same calendar dates. The gap flips only when you compare an Indiana Eastern city with a place that does not change clocks—Arizona is the common mainland case—or when software maps a ZIP code to the wrong county zone.
Northwest Indiana cities such as Gary and Hammond follow Central so they stay aligned with the Chicago metro; South Bend, still in Indiana but on Eastern, is one hour ahead of Chicago. Southwest, Evansville is Central while Bloomington (Eastern) is one hour ahead. Calendar invites that say only “Indiana time” without a city are ambiguous. Prefer a named city, or convert with EST to CST / CST to EST.
Historically, Indiana’s zone map shifted several times in the twentieth century; the current Eastern-majority / Central-pocket layout has been stable for years under DOT boundary rules. County-level detail is beyond this page’s static mainland map—use a city clock or converter when the meeting is near a zone line.
What time zones do U.S. territories use?
The populated territories on this page do not observe U.S. mainland Daylight Saving Time. Their offsets stay fixed all year, so the gap versus New York or Los Angeles changes when the mainland springs forward or falls back.
Puerto Rico and the U.S. Virgin Islands use Atlantic Standard Time (AST, UTC-4) via America/Puerto_Rico. In winter, AST matches Eastern Standard Time; from mid-March through early November, Eastern switches to EDT (UTC-4) while Puerto Rico stays on UTC-4, so San Juan and New York often show the same wall-clock hour during mainland daylight months. A recurring “9:00 a.m. ET” invite is usually fine for San Juan in summer, but in winter it is 10:00 a.m. in Puerto Rico unless the invite is tied to Atlantic time explicitly.
Guam and the Northern Mariana Islands use Chamorro Standard Time (ChST, UTC+10) via Pacific/Guam / Pacific/Saipan. That puts them roughly a day ahead of the U.S. West Coast for many business hours: when it is Monday afternoon in California, it is already Tuesday morning on Guam. Mainland Monday standups at 9:00 a.m. Pacific land in the small hours on Guam; late Pacific evenings are more usable for Guam morning.
American Samoa uses Samoa Standard Time (SST, UTC-11) via Pacific/Pago_Pago. It sits west of the Date Line relative to many Pacific neighbors and is one hour behind Hawaii (HST, UTC-10). Cross-territory calls between Pago Pago and Honolulu are a fixed one-hour gap; calls to the mainland span eleven or more hours depending on the U.S. zone and DST.
Hawaii is a state, not a territory, but it shares the no-DST pattern (HST, UTC-10). Uninhabited outlying areas such as Wake Island or Baker Island have official offsets on this page’s overview table but no live clocks. For Hawaii–East Coast pairs see HST to EST; for mainland multi-city mixes use the World Meeting Planner with named cities rather than a single “U.S. time” label.
What is the East Coast to West Coast time difference?
Across the contiguous United States, Eastern and Pacific are three hours apart year-round. Both coasts change clocks on the same federal DST dates, so the three-hour gap does not stretch or shrink when DST starts or ends. When it is 9:00 a.m. in New York, it is 6:00 a.m. in Los Angeles or Seattle; when it is noon Pacific, it is 3:00 p.m. Eastern.
Central Time sits one hour behind Eastern and one hour ahead of Mountain; Mountain sits one hour behind Central and one hour ahead of Pacific (except Arizona in summer, when Phoenix stays on MST and often matches Pacific Daylight Time). A coast-to-coast roster that also includes Denver or Chicago needs those intermediate offsets, not only the three-hour New York–Los Angeles rule.
For meetings that need both coasts in typical office hours, a practical overlap is roughly 1:00 p.m. to 5:00 p.m. Eastern (10:00 a.m. to 2:00 p.m. Pacific). Earlier than that forces a pre-9:00 a.m. start on the West Coast; later than about 5:00 p.m. Eastern pushes Pacific staff past mid-afternoon and Eastern staff into early evening. All-hands at 9:00 a.m. Eastern are 6:00 a.m. Pacific—workable for some teams, harsh for others. All-hands at 9:00 a.m. Pacific are noon Eastern, which is easier eastbound but may collide with East Coast lunch.
Sample anchors (Eastern → Pacific): 12:00 p.m. ET = 9:00 a.m. PT; 2:00 p.m. ET = 11:00 a.m. PT; 4:00 p.m. ET = 1:00 p.m. PT. Add Alaska (four hours behind Eastern in standard months, three behind during overlapping DST patterns relative to Eastern’s UTC offset) or Hawaii (five or six hours behind Eastern depending on the season) and the shared window shrinks further—prefer a dated converter instead of memorizing every case.
Broadcast and sports listings often say “8/7c” (Eastern / Central) without stating Pacific; Pacific viewers subtract three hours from Eastern, not two. Flight and hotel confirmations use local airport or property time. Dedicated converters: PST to EST, EST to PST. Guide: East Coast vs West Coast meeting times. Three or more cities: World Meeting Planner.
Where this page’s time data comes from
The clocks and zone labels on this page follow the IANA Time Zone Database (for example America/New_York, America/Chicago, America/Denver, America/Los_Angeles, America/Phoenix, Pacific/Honolulu). Most of the country observes Daylight Saving Time; Arizona, Hawaii, and several territories stay on standard time year-round. For a broader overview, see Time in the United States (opens in new tab).
