ShipZume
Guide

The six US time zones, and the places that break the pattern

The United States runs six time zones across its states and territories, and the map is messier than the four everybody remembers. Arizona ignores daylight saving, Hawaii never joined it, and more than a dozen states are split down the middle. This guide covers the whole picture, including the parts that catch out people booking calls.

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The zones, in order

Eastern Time (UTC−5, UTC−4 in summer) covers the north-east, the south-east and the eastern Midwest — about half the population. Central Time (UTC−6/−5) runs from the Gulf coast up through Chicago to the Dakotas. Mountain Time (UTC−7/−6) covers the Rockies, and Pacific Time (UTC−8/−7) the west coast. Alaska Time is UTC−9/−8, and Hawaii-Aleutian is UTC−10 with no seasonal change at all.

The complication is that state borders and zone borders rarely agree. Florida, Michigan, Indiana, Kentucky, Tennessee, Texas, Kansas, Nebraska, South Dakota, North Dakota, Idaho and Oregon all straddle a boundary. Saying "I'm in Florida" does not settle which hour you mean, because the western panhandle is on Central Time while Miami is on Eastern.

Arizona is the well-known exception on daylight saving: it stays on Mountain Standard Time all year, which means it matches Denver in winter and Los Angeles in summer. The Navajo Nation, which extends into Arizona, does observe daylight saving, so parts of the same state disagree with each other. Hawaii likewise never changes, so the gap between Honolulu and the mainland moves by an hour twice a year.

Key facts

Six zones in total

Eastern, Central, Mountain, Pacific, Alaska and Hawaii-Aleutian.

Eastern is the biggest

Roughly half the US population lives in it.

Arizona opts out

It stays on MST all year, so it matches Denver in winter and Los Angeles in summer.

Hawaii never changes

UTC−10 year-round, so the mainland gap shifts twice a year.

A dozen states are split

Including Florida, Texas, Indiana, Kentucky and Tennessee.

Clocks change in March and November

Second Sunday in March, first Sunday in November.

How to get it right

1

Ask for the city, not the state

A split state does not tell you which zone someone is in.

2

Note the summer exception

Arizona and Hawaii do not move, so their gaps change instead.

3

Use the IANA name in systems

America/New_York, not EST, which is only half the year.

4

Diary the two transition Sundays

March and November are when standing calls drift.

Questions people ask

Six in the states and territories people usually mean: Eastern, Central, Mountain, Pacific, Alaska and Hawaii-Aleutian. Counting outlying territories such as Guam and American Samoa adds more.

Keep reading

Daylight saving explained

Which countries change their clocks, when they do it, and why the same two cities can be five hours apart one week and six the next.

UTC, GMT and Zulu time

What UTC actually is, how it differs from GMT, why aviation says Zulu, and when the distinction matters.

Scheduling across time zones

A practical method for booking meetings across zones: finding the overlap, rotating the pain, and stopping recurring calls from drifting.

Convert between US zones

Every domestic pair has a page with the standard and daylight answers.

Open the converters