Coordinated Universal Time UTC - Greenwich Mean Time GMT Offset
Coordinated Universal Time (UTC) is used as the official world reference for time. Coordinated Universal Time replaced the use of Greenwich Mean Time (GMT) in 1972. You will often see time zones represented similar to UTC - 5h or GMT - 5h. In this example the (-5h) refers to that time zone being five hours behind UTC or GMT and so forth for the other time zones. UTC+5h or GMT +5h would refer to that time zone being five hours ahead of UTC of GMT and so forth for the other time zones.
The usage of UTC and GMT is based upon a twenty four hour clock, similar to military time, and is based upon the 0 degrees longitude meridian, referred to as the Greenwich meridian in Greenwich, England.
Coordinated Universal Time is based on cesium-beam atomic clocks, with leap seconds added to match earth-motion time, where as Greenwich Mean Time is based upon the Earth's rotation and celestial measurements. Coordinated Universal Time is also known Zulu Time or Z time.
In areas of the United States that observe Daylight Saving Time local residents will move their clocks ahead one hour when Daylight Saving Time begins. As a result, their UTC or GMT offset would change from UTC -5h or GMT - 5h to UTC -4h or GMT - 4h. In places not observing Daylight Saving Time the local UTC or GMT offset will remain the same year round. Arizona, Puerto Rico, Hawaii, U.S. Virgin Islands and American Samoa do not observe Daylight Saving Time.
In the United States Daylight Saving Time begins at 2:00 a.m. local time on the second Sunday in March. On the first Sunday in November areas on Daylight Saving Time return to Standard Time at 2:00 a.m. The names in each time zone change along with Daylight Saving Time. Eastern Standard Time (EST) becomes Eastern Daylight Time (EDT), and so forth. A new federal law took effect in March 2007 which extends Daylight Saving Time by four weeks.
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), Alaskan 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.
| Coordinated Universal Time (UTC) | Greenwich Mean Time (GMT) |
| Friday 11/22/24 03:06 PM UTC/GMT+00:00 |
Friday 11/22/24 03:06 PM UTC/GMT+00:00 |
United States GMT/UTC Offsets |
|||
| Time Zone in United States | Examples of places in the United States using these Time Zones | UTC Offset Standard Time |
UTC Offset Daylight Saving Time |
| Atlantic | Puerto Rico, US Virgin Islands | UTC - 4h | N/A |
| Eastern | Connecticut, Delaware, Florida, Georgia, part of Indiana, part of Kentucky, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, part of Tennessee, Vermont, Virginia, West Virginia and Washington, D.C. | UTC - 5h | UTC - 4h |
| Central | Alabama, Arkansas, Florida, Illinois, part of Indiana, Iowa, part of Kansas, part of Kentucky, Louisiana, part of Michigan, Minnesota, Mississippi, Missouri, Nebraska, North Dakota, Oklahoma, part of South Dakota, part of Tennessee, most of Texas, and Wisconsin | UTC - 6h | UTC - 5h |
| Mountain | Arizona*, Colorado, part of Idaho, part of Kansas, Montana, part of Nebraska, New Mexico, part of North Dakota, part of Oregon, part of South Dakota, part of Texas, Utah, and Wyoming | UTC - 7h | UTC - 6h * n/a for Arizona except in the Navajo Nation which does observe daylight saving time. |
| Pacific | California, part of Idaho, Nevada, most of Oregon, Washington | UTC - 8h | UTC - 7h |
| Alaska | Alaska and a portion of the Aleutian Islands that is east of 169 degrees 30 minutes west longitude observes the Alaska Time Zone. | UTC - 9h | UTC - 8h |
| Hawaii - Aleutian Unofficially often referred to as Hawaii Time Zone |
Hawaii and a portion of the Aleutian Islands that is west of 169 degrees 30 minutes west longitude observes the Hawaii-Aleutian Standard Time Zone. Although Hawaii does not observe daylight saving time the Aleutian Islands do observe daylight saving time. | UTC - 10h | UTC - 9h Hawaii does not observe daylight saving time. A portion of the Aleutian Islands which observes the Hawaii - Aleutian time zone does observe daylight saving time. |