US Time Zones by State: Full List and Split States

The nine zones

Federal law, 15 U.S.C. 261, sets nine standard time zones and their offsets from Coordinated Universal Time. The Department of Transportation draws their borders in 49 CFR Part 71. During daylight saving time, every zone that observes it moves one hour ahead, so Eastern goes from UTC−5 to UTC−4.

Which abbreviation to write in a date, ET, EST or EDT, is its own question, answered in EST vs EDT vs ET.

Every state and its time zone

The main zone comes first. For the 14 split states, the last column says which part uses the second zone.

By main zone, 22 Eastern, 16 Central, 7 Mountain, and 4 Pacific, counting the District of Columbia with the 50 states. Alaska and Hawaii each have their own zone.

The 14 states in two zones

The boundary lines in Part 71 are written mostly as county lines, rivers and state borders, not as straight meridians, so they zigzag. Four of them cross state interiors:

• Eastern and Central (49 CFR 71.5): Michigan, where the western Upper Peninsula counties along Wisconsin are Central; Indiana, with a block of counties in the northwest and another in the southwest on Central time; Kentucky, roughly split down the middle; Tennessee, where only the east is Eastern; and Florida, where the Panhandle west of the Apalachicola River is Central.
• Central and Mountain (71.7): North Dakota, South Dakota and Nebraska, each with its western part on Mountain time; Kansas, where only a few counties on the Colorado line are Mountain; and Texas, where El Paso and Hudspeth counties in the far west are Mountain.
• Mountain and Pacific (71.9): Idaho, whose northern part beyond the Salmon River is Pacific; Oregon, where most of Malheur County is Mountain; and Nevada, where only the City of West Wendover, next to Utah, is Mountain.
• Alaska and Hawaii-Aleutian (71.12): the Aleutian Islands west of 169°30′ W are one hour behind the rest of Alaska.

In a split state, check the county, not the state, before setting a meeting. A call at 9:00 in eastern Florida is 8:00 in the western Panhandle. The time zone converter works from city names, which avoids the guesswork.

Arizona and Hawaii: no daylight saving time

Under 15 U.S.C. 260a, clocks move ahead at 2 a.m. on the second Sunday in March and back on the first Sunday in November. A state that lies entirely in one zone may exempt itself by law, and a split state may exempt the area in one of its zones. NIST lists Arizona and Hawaii as the states that do not observe daylight saving time, along with Puerto Rico, the U.S. Virgin Islands, Guam and American Samoa. Inside Arizona, the Navajo Indian Reservation does observe it, so in summer it is an hour ahead of the rest of the state.

Because the other states move their clocks and these do not, the gap to them changes twice a year. The table shows how far each zone is from Eastern time, in winter and in summer.

Arizona and Hawaii fall one hour further behind New York in summer, and Puerto Rico goes from one hour ahead to the same time. The exact switch dates for this year are in Daylight Saving Time 2026.

A worked example: Denver to Phoenix

Denver and Phoenix are both in the Mountain zone, but only Denver changes its clocks. Take a flight that leaves Denver at 9:00 a.m. local time and takes 2.5 hours. In January both cities are on UTC−7, so it lands at 11:30 a.m. Phoenix time. In July Denver is on Mountain Daylight Time, UTC−6, while Phoenix stays on UTC−7, so the same flight lands at 10:30 a.m. Phoenix time. The schedule looks an hour shorter in summer, and a connection booked in Denver time can be off by an hour on the ground. The same thing happens on any trip into Hawaii, Puerto Rico or the U.S. territories in the Pacific.

Puerto Rico, Guam and the other territories

Three of the nine zones exist only for territories. Puerto Rico and the U.S. Virgin Islands are on Atlantic time, UTC−4, and do not observe daylight saving time, so they match the East Coast from March to November and are an hour ahead of it in winter. American Samoa is on Samoa time, UTC−11, the furthest behind UTC of all U.S. zones. Guam and the Northern Mariana Islands are on Chamorro time, UTC+10, across the date line. Between Guam and American Samoa the clocks are 21 hours apart, so a Monday morning in Guam is still Sunday in American Samoa.

Scheduling across zones

The continental United States spans four zones, so a 9:00 a.m. Eastern call is 6:00 a.m. on the West Coast. A window that works for a team from Boston to Seattle is roughly noon to 5:00 p.m. Eastern. Add Hawaii and the overlap with the East Coast shrinks to a few hours, and in summer it shrinks by one more. The meeting planner lines up working hours for several cities at once. Writing times on a 24-hour clock removes the a.m. and p.m. mix-up on top of the zone math; the military time converter turns 1400 into 2:00 p.m. and back.

Rules of thumb

• Write the zone with every time in an invitation, and the city if the state is split.
• Arizona keeps UTC−7 all year: Denver time in winter, Los Angeles time in summer.
• Hawaii keeps UTC−10 all year: five hours behind New York in winter, six in summer.
• Guam and the Northern Mariana Islands are on UTC+10, which is 15 hours ahead of Eastern Standard Time.

Frequently asked questions

Sources

• 15 U.S.C. 261: the nine standard time zones and their offsets from UTC
• 15 U.S.C. 260a: DST from the second Sunday in March to the first Sunday in November; a state entirely in one zone may exempt itself; a split state may exempt the area in one zone
• 49 CFR 71.1: Part 71 prescribes the limits of the nine standard time zones
• 49 CFR 71.3: Atlantic zone, including Puerto Rico
• 49 CFR 71.5: Eastern-Central boundary through Michigan, Indiana, Kentucky, Tennessee and Florida
• 49 CFR 71.7: Central-Mountain boundary through North Dakota, South Dakota, Nebraska, Kansas and Texas
• 49 CFR 71.9: Mountain-Pacific boundary through Idaho, Oregon and the City of West Wendover, Nevada
• 49 CFR 71.11 and 71.12: Alaska zone; Hawaii-Aleutian zone includes Hawaii and the Aleutians west of 169°30′ W
• 49 CFR 71.13 and 71.14: Samoa zone; Chamorro zone for Guam and the Northern Mariana Islands
• NIST: Daylight saving time (not observed in Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands and Arizona, except the Navajo Indian Reservation)

Written by Tobias. Updated November 2, 2026.