Time Zones & UTC Hub

Arizona (except for the Navajo Nation) and Hawaii are the two US states that do not participate in Daylight Saving Time. They remain on Mountain Standard Time (MST, UTC-7) and Hawaii Standard Time (HST, UTC-10) year-round.

Additionally, the US territories of Puerto Rico, Guam, American Samoa, the US Virgin Islands, and the Northern Mariana Islands never observe daylight saving shifts.

Coordinated Universal Time (UTC) is a high-precision atomic time standard synchronized by hundreds of atomic clocks located worldwide. It never changes with the seasons and forms the foundation for digital civil timekeeping and aviation.

Greenwich Mean Time (GMT) is an astronomical solar time zone based on the mean solar time at the Royal Observatory in Greenwich, London. In civilian practice, UTC and GMT display the identical hour and minute, but UTC is the scientifically recognized standard.

Under federal law, the US Department of Transportation (DOT) is responsible for establishing and changing time zone boundaries. The DOT draws boundaries to facilitate regional trade, local school bus routes, and economic ties to neighboring metropolitan hubs.

For example, the western tip of Texas (El Paso) observes Mountain Time because its trade routes connect closely with New Mexico and Chihuahua, Mexico, while the rest of Texas operates on Central Time. Florida, Tennessee, Indiana, and Nebraska also feature official county-level time zone boundaries.

Nepal operates on Nepal Time (NPT), which has a 45-minute fractional offset: UTC+5:45. It is calibrated precisely to the longitude meridian passing through Mount Gauri Sankar.

Other notable fractional time zones include India and Sri Lanka (UTC+5:30), Newfoundland in Canada (UTC-3:30), Iran (UTC+3:30), and the Chatham Islands of New Zealand (UTC+12:45).