US Time Zones

US Time Zones Overview

The United States spans six time zones, covering 50 states and several territories across the Pacific and Atlantic oceans. The continental US uses four primary time zones, while Alaska and Hawaii each have their own.

• Eastern Time (ET) - UTC-5 / UTC-4 (DST). Used along the entire East Coast, from Maine down to Florida, and as far west as parts of Indiana, Michigan, and Ohio.
• Central Time (CT) - UTC-6 / UTC-5 (DST). Covers a large swath of the Midwest and South, including Texas, Illinois, Minnesota, and Alabama.
• Mountain Time (MT) - UTC-7 / UTC-6 (DST). Encompasses the Rocky Mountain states like Colorado, Utah, Montana, and New Mexico. Arizona stays on standard Mountain Time year-round.
• Pacific Time (PT) - UTC-8 / UTC-7 (DST). The westernmost zone of the contiguous US, used in California, Oregon, Washington, and Nevada.
• Alaska Time (AKT) - UTC-9 / UTC-8 (DST). Covers most of Alaska except the Aleutian Islands.
• Hawaii-Aleutian Time (HAT) - UTC-10. Hawaii does not observe DST, so it remains UTC-10 year-round. The Aleutian Islands in Alaska follow this zone during standard time but switch to Alaska Time during DST.

Time Zone Boundaries in the US

Time zone boundaries in the United States do not always follow state lines. The federal government, through the Department of Transportation, establishes time zone rules, and local jurisdictions can petition for changes. This means that several states are split between two time zones:

• Florida - The panhandle region (west of the Apalachicola River) operates on Central Time, while the rest of the state is on Eastern Time.
• Indiana - Most of the state is on Eastern Time, but northwestern and southwestern counties observe Central Time.
• Tennessee - The eastern portion is on Eastern Time, while the western counties, including Memphis, are on Central Time.
• Kentucky - Eastern Kentucky is on Eastern Time, while the western part near Louisville and Bowling Green uses Central Time.
• North Dakota - The southwestern corner around Dickinson and the Oil Patch region uses Mountain Time, while the rest of the state is on Central Time.
• South Dakota - The counties west of the Missouri River are on Mountain Time, while those to the east are on Central Time.

These splits can create confusing situations, especially for travelers, commuters, and businesses near zone boundaries. Some cities, like Evansville, Indiana, and Columbus, Georgia, sit right on the edge and must coordinate with both adjacent zones daily.

Daylight Saving Time in the United States

Most of the United States observes Daylight Saving Time (DST), which shifts clocks forward one hour during the warmer months. The clocks spring forward on the second Sunday in March at 2:00 AM local time and fall back on the first Sunday in November at 2:00 AM local time. This effectively moves one hour of daylight from morning to evening.

Under federal law, states may opt out of DST by passing a state legislature bill, but they cannot permanently adopt DST without federal approval. Currently, two states do not observe DST:

• Arizona - Most of Arizona stays on Mountain Standard Time (UTC-7) year-round. The Navajo Nation, which spans parts of Arizona, New Mexico, and Utah, does observe DST to maintain consistency across its territory.
• Hawaii - Hawaii remains on Hawaii-Aleutian Standard Time (UTC-10) throughout the year, as its tropical location means DST would offer minimal benefit.

In recent years, the Sunshine Protection Act has gained bipartisan support in Congress. This legislation would make DST permanent nationwide, eliminating the biannual clock changes. The bill passed the Senate unanimously in 2022 but has not yet been signed into law. If enacted, clocks would spring forward one final time and remain there permanently.

US territories including Puerto Rico, the US Virgin Islands, Guam, American Samoa, and the Northern Mariana Islands do not observe DST and remain on their standard time offsets year-round.

US Territories and Their Time Zones

Beyond the 50 states, the United States has several territories and possessions, each operating in its own time zone:

• Puerto Rico - Atlantic Standard Time (AST, UTC-4) year-round. The island does not observe DST. San Juan and the rest of the territory share the same time as the US East Coast during standard time.
• US Virgin Islands - Also on Atlantic Standard Time (AST, UTC-4), the same as Puerto Rico. The territory, including St. Thomas, St. Croix, and St. John, does not observe DST.
• Guam - Chamorro Standard Time (ChST, UTC+10). Guam is one of the closest US territories to the International Date Line. It does not observe DST and is 14-15 hours ahead of the US East Coast depending on the time of year.
• American Samoa - Samoa Standard Time (SST, UTC-11). Located near the International Date Line, American Samoa is one of the last places on Earth to see each new calendar day. It does not observe DST.
• Northern Mariana Islands - Chamorro Standard Time (ChST, UTC+10), the same as Guam. The CNMI does not observe DST.

Current Time Across the US

The table below shows the current time in major US cities and territories. Use it to quickly compare times across different zones when scheduling calls, flights, or meetings.

City	Time Zone	UTC Offset
New York, NY	Eastern (ET)	UTC-5 / UTC-4
Chicago, IL	Central (CT)	UTC-6 / UTC-5
Denver, CO	Mountain (MT)	UTC-7 / UTC-6
Los Angeles, CA	Pacific (PT)	UTC-8 / UTC-7
Anchorage, AK	Alaska (AKT)	UTC-9 / UTC-8
Honolulu, HI	Hawaii-Aleutian (HAT)	UTC-10
Phoenix, AZ	Mountain (No DST)	UTC-7
San Juan, PR	Atlantic (AST)	UTC-4
Hagatna, GU	Chamorro (ChST)	UTC+10
Pago Pago, AS	Samoa (SST)	UTC-11

Fun Facts About US Time Zones

• Indiana's DST confusion: Indiana was the last state in the continental US to fully adopt DST. Before 2006, only some counties observed it, creating a patchwork of time zones within a single state. The current system, with most of Indiana on Eastern Time and DST, was established in 2006.
• 19-hour time difference: When it is noon on the US East Coast, it is already 7:00 AM the next day in American Samoa (UTC-11), but only 10:00 AM in Guam (UTC+10) — a span of nearly 19 hours across all US jurisdictions.
• Daylight saving was for energy, not farming: Despite the common myth, DST was not originally created for farmers. It was first implemented during World War I to conserve coal, and reinstated during World War II for the same reason. Farmers have historically opposed DST because it disrupts their routines based on sunlight.
• Four time zones in Texas: Texas is so large geographically that it spans two time zones. El Paso and far West Texas operate on Mountain Time, while the rest of the state is on Central Time — meaning Texans in different cities can be an hour apart.
• The Navajo Nation exception: Arizona refuses to observe DST, but the Navajo Nation, which extends across three states, does observe it. This creates a unique situation where the Hopi Reservation, which is entirely surrounded by the Navajo Nation in Arizona, does not observe DST, resulting in time zone "islands" within the state.