Time Zone Codes in the United States
Time Zone Codes are a method of abbreviating the name of a Time Zone. As an example, in the United States Eastern Standard Time is abbreviated with the Time Zone Code EST. When daylight saving time is in effect Eastern Daylight Time is abbreviated with the Time Zone Code EDT. This type of time zone code abbreviation is used for each time zone code in the United States.
Time Zone Codes offer many advantages over writing the full name of the Time Zone. They are shorter and can be used more effectively to express a time zone such as 2:00 pm EST. Compare this to writing the full name of the time zone which would be 2:00 pm Eastern Standard Time. In verbal communications the opposite is true. It is often preferable for purposes of clarity to use the full time zone name rather than the time zone code. As an example, you may hear on the radio or television a program time announced as 5:00 Eastern Standard Time rather than 5:00 EST.
The United States uses nine standard time zones. From east to west they are Atlantic Standard Time (AST), Eastern Standard Time (EST), Central Standard Time (CST), Mountain Standard Time (MST), Pacific Standard Time (PST), Alaska Standard Time (AKST), Hawaii-Aleutian Standard Time (HST), Samoa standard time (UTC-11) and Chamorro Standard Time (UTC+10). View the standard time zone boundaries.
The military, as well as commercial aviation, use a different time zone code system, often referred to as Military Time Zone Codes. For more information about Military Time Zones view this page.
The time zone code for Coordinated Universal Time is (UTC) and the time zone code for Greenwich Mean Time is (GMT). The (-8h) in PST or Pacific Standard Time refers to that time zone being eight hours behind UTC or GMT and so forth for the other Time Zones.
Time Zone Codes used in the United States
| CODE | UNITED STATES TIME ZONE CODES | UTC OFFSET |
| AST | ATLANTIC STANDARD TIME | UTC - 4 |
| EST | EASTERN STANDARD TIME | UTC - 5 |
| EDT | EASTERN DAYLIGHT TIME | UTC - 4 |
| CST | CENTRAL STANDARD TIME | UTC - 6 |
| CDT | CENTRAL DAYLIGHT TIME | UTC - 5 |
| MST | MOUNTAIN STANDARD TIME | UTC - 7 |
| MDT | MOUNTAIN DAYLIGHT TIME | UTC - 6 |
| PST | PACIFIC STANDARD TIME | UTC - 8 |
| PDT | PACIFIC DAYLIGHT TIME | UTC - 7 |
| AKST | ALASKA TIME | UTC - 9 |
| AKDT | ALASKA DAYLIGHT TIME | UTC - 8 |
| HAST | HAWAII-ALEUTIAN STANDARD TIME | UTC - 10 |
| HADT | HAWAII-ALEUTIAN DAYLIGHT TIME | UTC - 9 |
| SST | SAMOA STANDARD TIME | UTC - 11 |
| SDT | SAMOA DAYLIGHT TIME | UTC - 10 |
| CHST | CHAMORRO STANDARD TIME | UTC +10 |
