Ask most Americans how many time zones the US has, and you'll usually get one of two answers: "four" (thinking of the continental US) or "six" (remembering Alaska and Hawaii too). Both answers are reasonable — and both are incomplete. By federal law, the United States and its territories use nine standard time zones.
The six you'd expect
Across the 50 states, there really are six time zones:
- Eastern Time (UTC-5 standard / UTC-4 daylight) — the most populous zone, covering the East Coast from Maine to Florida and inland to around the Great Lakes.
- Central Time (UTC-6 / UTC-5) — the Midwest and much of the South, from Texas up through Illinois.
- Mountain Time (UTC-7 / UTC-6) — the Rockies, from Montana down through Arizona and New Mexico.
- Pacific Time (UTC-8 / UTC-7) — the West Coast, California to Washington.
- Alaska Time (UTC-9 / UTC-8) — nearly all of Alaska.
- Hawaii-Aleutian Time (UTC-10) — Hawaii and the western Aleutian Islands, with no Daylight Saving Time observed.
These six are what most "how many time zones does the US have" answers stop at — and if you're only thinking about the 50 states, six is the right number.
The three most people forget
The full federal count, under Title 49 of the Code of Federal Regulations, adds three more zones used by US territories:
- Atlantic Time (UTC-4) — Puerto Rico and the US Virgin Islands.
- Samoa Time (UTC-11) — American Samoa.
- Chamorro Time (UTC+10) — Guam and the Northern Mariana Islands, on the other side of the International Date Line.
That brings the legal total to nine. None of these three observe Daylight Saving Time, which is also true of Hawaii and (mostly) Arizona among the state-based zones — so out of nine official US time zones, only four actually shift their clocks twice a year.
All nine, at a glance
| Zone | Standard UTC offset | Observes DST? | Where |
|---|---|---|---|
| Chamorro | UTC+10 | No | Guam, Northern Mariana Islands |
| Samoa | UTC-11 | No | American Samoa |
| Hawaii-Aleutian | UTC-10 | No | Hawaii, western Aleutian Islands |
| Alaska | UTC-9 | Yes | Most of Alaska |
| Pacific | UTC-8 | Yes | California, Washington, Nevada, most of Oregon |
| Mountain | UTC-7 | Yes (except most of Arizona) | Colorado, Utah, New Mexico, most of Arizona |
| Central | UTC-6 | Yes | Texas, Illinois, and much of the Midwest/South |
| Eastern | UTC-5 | Yes | New York, Florida, and most of the East Coast |
| Atlantic | UTC-4 | No | Puerto Rico, US Virgin Islands |
Even that isn't quite the whole map
A handful of uninhabited or minimally populated US possessions sit outside all nine official zones entirely. Baker Island and Howland Island, far out in the Pacific, are assigned UTC-12 — sometimes informally called "Anywhere on Earth" time, since it's the last time zone on Earth to reach any given calendar date. Wake Island, on the opposite side of the date line, uses UTC+12. Neither has a permanent population, so they rarely come up in everyday scheduling — but they're technically part of the full picture.
Why this actually matters
Beyond trivia, the practical takeaway is this: if you're scheduling with someone in Puerto Rico, Guam, or American Samoa, don't assume they fall into one of the "big six" continental zones — they don't, and treating them as if they do can put you multiple hours off. The US spans a full 24-hour range across its territories, from Guam (10 hours ahead of UTC) to American Samoa (11 hours behind) — meaning it's possible for two people to both be "in the United States" and be on completely different calendar dates at the same moment.
Whichever US location you're working with, the time zone converter resolves the exact current offset by city — including the territories most guides forget to mention.
Frequently asked questions
How many time zones does the US actually have?
Nine. Six cover the 50 states — Eastern, Central, Mountain, Pacific, Alaska and Hawaii–Aleutian — and three more cover the territories: Atlantic for Puerto Rico and the US Virgin Islands, Samoa for American Samoa, and Chamorro for Guam and the Northern Mariana Islands.
Do all nine US time zones change their clocks?
No. Atlantic, Samoa and Chamorro Time do not observe Daylight Saving Time at all, and neither does Hawaii or most of Arizona. Only a minority of the nine official zones shift their clocks twice a year, so assuming the whole country springs forward together will put you an hour out.
What's the widest time gap between two places in the United States?
A full 24 hours across the territories, from Guam at UTC+10 to American Samoa at UTC−11. That means two people can both be “in the United States” and be on completely different calendar dates at the same moment — the widest span of any country's inhabited territory.
Are there US locations outside the nine official time zones?
Yes. A few uninhabited possessions sit outside all nine. Baker Island and Howland Island in the Pacific are assigned UTC−12, the last place on Earth to reach any calendar date, and Wake Island uses UTC+12. Neither has a permanent population, so they rarely matter for scheduling.