US Time Zones Table
| Time zone | Standard | DST | Where observed |
|---|---|---|---|
| Atlantic | UTC−04:00 | (none) | Puerto Rico, U.S. Virgin Islands |
| Eastern | UTC−05:00 | UTC−04:00 | CT DE GA ME MD MA NH NJ NY NC OH PA RI SC VT VA DC WV + parts of FL IN KY MI TN |
| Central | UTC−06:00 | UTC−05:00 | AL AR IL IA LA MN MS MO OK WI + parts of FL IN KS KY MI NE ND SD TN TX |
| Mountain | UTC−07:00 | UTC−06:00 | CO MT NM UT WY + parts of ID KS NE NV ND OR SD TX (AZ skips DST except Navajo Nation) |
| Pacific | UTC−08:00 | UTC−07:00 | CA WA + parts of ID NV OR |
| Alaska | UTC−09:00 | UTC−08:00 | Alaska (except the Aleutians west of 169°W) |
| Hawaii–Aleutian | UTC−10:00 | UTC−09:00 (Aleutians only) | Hawaii (no DST), part of Alaska |
| Samoa | UTC−11:00 | (none) | American Samoa |
| Chamorro | UTC+10:00 | (none) | Guam, Northern Mariana Islands |
The United States runs on nine time zones, and the table's shape tells the story: four contiguous giants (Eastern, Central, Mountain, Pacific) created by the railroads in 1883 and codified by the Standard Time Act of 1918, plus five outliers that follow the flag rather than the continent - Alaska at UTC-9, Hawaii-Aleutian at UTC-10, and the Pacific territories wrapped around the date line, from Samoa at UTC-11 to Guam and the Northern Marianas at UTC+10.
The DST column is where the exceptions cluster. Federal law (15 U.S.C. §260) springs every zone forward on the second Sunday of March and back on the first Sunday of November - but it is opt-out law, and the opt-outs are the famous ones: Hawaii dropped it in 1945 because tropical day length barely moves, Arizona skips it statewide except that the Navajo Nation inside the state does observe it, and Puerto Rico, the Virgin Islands, American Samoa, Guam and the Marianas never touch it.
Reading offsets beats memorizing maps: Eastern is UTC-5 standard and UTC-4 in summer, so noon in New York is 9 a.m. in Los Angeles year-round once you track the DST window. The table's honest limit is state borders - thirteen states straddle two zones, and the split lines run through counties, not meridians - which is why the Where column names the whole-state rows first and flags the partial ones.
How to use
- Find your zone's row and read the standard offset: subtract it from UTC to get local standard time; during the DST window (second Sunday of March to first Sunday of November) add one hour to the zones whose DST column shows an offset.
- Handle the two opt-outs correctly: Arizona stays on UTC-7 all year (so in summer it matches Pacific daylight time, not Mountain daylight), and Hawaii stays on UTC-10 all year - three hours behind New York in winter, six in summer.
- Cross the date line carefully: Guam and the Northern Marianas run Chamorro Time at UTC+10 - a full 18 hours ahead of American Samoa's UTC-11 across only about 1,500 miles, which is why the territory pair brackets the entire offset table.
- For a live conversion, pair this table with the time zone converter; for the exact March and November switch dates of any year, use the daylight saving dates table - the rules are annual and this table stays timeless.
Frequently asked questions
Why doesn't Arizona observe daylight saving time?
Arizona opted out in 1967: in a desert, extending evening daylight means more heat, not more useful light, so Phoenix stays on Mountain Standard Time year-round. The exception inside the exception is the Navajo Nation, which does spring forward - so in summer Arizona holds two clocks, and the Hopi reservation inside the Navajo Nation holds the third state of the world's most famous time-zone donut.
How many time zones does the US have in total?
Nine: Eastern, Central, Mountain and Pacific in the contiguous states; Alaska and Hawaii-Aleutian for the far states; and Atlantic (Puerto Rico and the US Virgin Islands), Samoa and Chamorro for the territories. Thirteen states straddle two zones, which is why county borders, not meridians, decide the clock in places like Florida, Texas and Oregon.
What is the difference between EST and EDT?
EST is Eastern Standard Time, UTC-5 - the geography; EDT is Eastern Daylight Time, UTC-4 - the policy, in force from the second Sunday of March to the first Sunday of November. The same S/D pattern applies across Central, Mountain and Pacific, which is why this table lists standard offsets and lets the DST column carry the summer shift.
Which US territory is furthest ahead in time?
Guam and the Northern Mariana Islands on Chamorro Time, UTC+10 - eighteen hours ahead of American Samoa at UTC-11, even though the two territories sit only about 1,500 miles apart. The pair brackets the whole table because the International Date Line passes between them: Guam is often on tomorrow before Samoa finishes today.