If you’re curious about the way the world spins and how we, in so many different places around the globe, tell time, then you’ve probably wondered: How many time zones are there in the United States?
According to Time and Date.com, the United States operates under multiple time zones. The bulk of the country is spread between 6 time zones, while dependencies such as Puerto Rico, Guam, and the U.S. Minor Outlying Islands all bring the total of time zones to 11.
In this article, we will show you not only the grand total of time zones across the United States and how they are established, but what the timeline of time zones in the United States have been throughout history. We’ll even break down which dependencies use which time zones!
Main Standard Time Zones in the United States
Currently, all time zones in the United States and their territories are offsets of Coordinated Universal Time, which is also known as “UTC.” UTC is, in the civil world (which is how business is conducted) a basis for one 24-hour time period known as a day. However, thanks to longitudinal differences, countries around the globe are still divided into separate time zones.
The United States, for example, has been divided into four standard time zones in the month of November in the year 1883. Ever since the 60s, these time zones have been determined by the United States Department of Transportation.
The United States four standard time zones are:
- Pacific Time – Abbreviated often as “PT,” or “PD” during Daylight Savings, this time zone is 8 hours behind UTC and accounts for the Western United States. It is changed twice each year to jump either an hour ahead of UTC or an hour behind.
- Central Time – Abbreviated normally as “CST” until Daylight Savings, when it switches to “CDT,” Central Time is usually six hours behind UTC. It accounts for the eastern United States, and a grand total of one third of the United States population live in this time zone.
- Mountain Time – Abbreviation often as “MST” or “MDT” during Daylight Saving Time, Mountain Time is the other time zone for the Western United States which reaches up into parts of Canada, as well, such as Alberta and the Northwest Territories. It is 7 hours behind UTC.
- Eastern Time – Known as “EST” and changed to “EDT” during Daylight Savings, Eastern Time is five hours behind the reading of UTC. It covers the Eastern United States, but is also used in Canada as well as countries in the Caribbean such as Haiti and the Bahamas. Panama also uses EST for the entire year!
Each of these time zones are typically called by their usual name no matter which time of year it is, though other countries (like Great Britain) may give Daylight Savings Time zones a different name. For the United States, time simply changes without a shift in titles! Most Daylight Saving Times in the United States begin in March.
The only exceptions to these are Hawaii-Aleutian Daylight Time and Alaska Daylight Time, which are 9 and 8 hours behind UTC, respectively!
However, these four time zones are not the only ones counted when trying to number the total time zones in the United States. This is because the USA lays claim to several territories, the locations of which are far enough away latitudinally to justify having time zones of their own.
These will be detailed in the list below:
- Samoa Standard Time
- Anywhere on Earth
- Atlantic Standard Time
- Wake Time
- Chamorro Standard Time
Let’s get a more in-depth look at what each of these time zones entails and which territories belonging to the United States are involved in them:
1. Samoa Standard Time
Samoa Standard Time, also known as SST, accounts for two territories living in the 11 total United States time zones. It is 11 hours behind UTC, and is followed by Unincorp. Unorg. Territory of American Samoa and the United States Minor Outlying Islands.
On Midway Island and American Samoa, Samoa Standard Time is used all year round!
2. Anywhere on Earth
This uniquely-named time zone is also called “AoE,” and applies to some of the other United States Minor Outlying Islands. It is known to be behind Coordinated Universal Time by 12 hours, and is only observed all year round by Baker Island.
This time zone is interesting because it is considered “theoretical,” and only sometimes applied to Baker Island and Howland Island in the United States territories because those land masses are the last places west of the International Date Line where dates can exist.
3. Atlantic Standard Time
Also known as AST, Atlantic Standard Time is four hours behind UTC and used by Unicorp. Org. Territories of the United States Virgin Islands and Puerto Rico. It is also used by four different provinces in the country of Canada, and is sometimes called the Atlantic Time Zone.
4. Wake Time
Wake Time is also known as “WAKT,” and is only used in the United States Minor Outlying Island of Wake Island. It is always 12 hours ahead of the UTC time on Wake Island!
5. Chamorro Standard Time
Chamorro Standard Time is sometimes referred to by the somewhat complex abbreviation of “ChST.” It is used in the Unincorp.org territory of Guam, as well as the Northern Mariana Islands. Chamorro Standard Time runs at ten hours ahead of Coordinated Universal Time.
Both Guam and the Northern Mariana Islands use ChST all year round!
To sum everything we’ve learned up, the United States has a grand total of 11 time zones. The main country uses 4 standard time zones, which are the Pacific, Eastern, Mountain, and Central. However, these are added to by Alaska Standard Time and Hawaii Standard Time. In addition, each of the main four switch to a new time zone during the summer season.
Finally, when adding the variances in time zones based on longitude in the United States dependencies and territories, the total of time zones comes to 11.