US Time Zones Explained: All 6 Zones and How They Work

The 50 United States span 6 time zones: Eastern, Central, Mountain, Pacific, Alaska, and Hawaii-Aleutian. If you include US territories (Puerto Rico, Guam, American Samoa, US Virgin Islands, Northern Mariana Islands), the total rises to 9.

The contiguous 48 states use 4 time zones: Eastern (UTC-5), Central (UTC-6), Mountain (UTC-7), and Pacific (UTC-8). Alaska adds a 5th zone (UTC-9), and Hawaii adds a 6th (UTC-10).

The US spans about 58 degrees of longitude, which is enough for nearly 4 standard hourly time zones. The addition of Alaska and Hawaii brings the count to 6 for the 50 states.

Eastern Time is the most populous US time zone. It covers 17 states fully and parts of 5 more. Major cities include New York, Boston, Philadelphia, Washington DC, Atlanta, Miami, Charlotte, Detroit, and Orlando.

During standard time, Eastern is UTC-5 (EST). During daylight saving time, it is UTC-4 (EDT). DST runs from the second Sunday of March to the first Sunday of November.

Eastern Time is the reference clock for US financial markets, television broadcasting, and many national scheduling conventions. When a US event says it starts at 8:00 PM ET, that is the time for the entire East Coast.

Central Time covers 17 states fully and parts of 8 more. Major cities include Chicago, Dallas, Houston, San Antonio, Minneapolis, Milwaukee, Kansas City, and New Orleans.

During standard time, Central is UTC-6 (CST). During DST, it is UTC-5 (CDT). Central Time is one hour behind Eastern Time.

The Central-Eastern boundary runs through states like Tennessee, Kentucky, Indiana, Michigan, Florida, and Alabama, where different cities within the same state may be in different time zones.

Mountain Time covers Colorado, Wyoming, Montana, Utah, New Mexico, and parts of Arizona, Idaho, Oregon, Kansas, Nebraska, North Dakota, South Dakota, Texas, and Oklahoma.

During standard time, Mountain is UTC-7 (MST). During DST, it is UTC-6 (MDT). Mountain Time is one hour behind Central and two hours behind Eastern.

Arizona is a notable exception: it does not observe DST and stays on Mountain Standard Time (UTC-7) year-round. However, the Navajo Nation in northeastern Arizona does observe DST.

Pacific Time covers California, Oregon, Washington, and parts of Idaho and Nevada. Major cities include Los Angeles, San Francisco, Seattle, Portland, San Diego, and Las Vegas.

During standard time, Pacific is UTC-8 (PST). During DST, it is UTC-7 (PDT). Pacific Time is 3 hours behind Eastern Time.

Pacific Time is the reference for the US entertainment industry, Silicon Valley, and West Coast business operations.

Alaska Time (UTC-9 standard, UTC-8 DST) covers most of Alaska. The Aleutian Islands that cross the International Date Line use Hawaii-Aleutian time instead.

Hawaii-Aleutian Time (UTC-10) covers Hawaii and the western Aleutian Islands. Hawaii does not observe DST. The western Aleutians do observe DST.

Hawaii is 5 hours behind Eastern Standard Time and 6 hours behind Eastern Daylight Time. This means a show that airs at 9:00 PM Eastern starts at 4:00 PM or 3:00 PM in Hawaii, depending on DST.

• Use city names instead of ambiguous timezone abbreviations.
• Repeat the selected time on booking confirmation pages.
• Check daylight saving changes before publishing event times.

All US time zones observe DST except Hawaii and most of Arizona. DST begins on the second Sunday of March (clocks spring forward at 2:00 AM) and ends on the first Sunday of November (clocks fall back at 2:00 AM).

During DST, all four contiguous US zones shift forward by one hour. The gap between them stays the same. Eastern stays 1 hour ahead of Central, 2 hours ahead of Mountain, and 3 hours ahead of Pacific.

The transition weeks can be confusing for scheduling with international partners. The US changes on different dates than Europe and Australia, creating temporary shifts in international time differences.

If your meeting includes participants from multiple US zones, the best window is 12:00 PM to 3:00 PM Eastern. That is 11:00 AM to 2:00 PM Central, 10:00 AM to 1:00 PM Mountain, and 9:00 AM to 12:00 PM Pacific.

For meetings that include Hawaii or Alaska, the window narrows. Hawaii's working hours (9 AM to 5 PM) correspond to 2:00 PM to 10:00 PM Eastern, which means the East Coast team would need to stay late.

Use the time zone converter to check the local time for every participant. For recurring meetings, document the timezone explicitly in the calendar invite.

The US has 6 time zones for the 50 states and 9 including territories. The four contiguous zones (Eastern, Central, Mountain, Pacific) are the most commonly used. All observe DST except Hawaii and most of Arizona.

When scheduling across US zones, always specify the timezone in your calendar invite. Write Eastern Time, not ET, and always include the UTC offset if there is any ambiguity.