Coordinated Universal Time (abbreviated to UTC) is the primary time standard by which the world regulates clocks and time. World time is added to or subtracted from the time at 0° longitude, which is not adjusted for daylight saving time.
|Time Zone||Time Examples||Standard Time||Daylight Time||Zone|
|Hawaii-Aleutian Time||06 AM–11 AM||HST (UTC–10:00)||HST (UTC–10:00)||Zone W|
|Alaska Time||07 AM–12 PM||AKST (UTC–09:00)||AKDT (UTC–08:00)||Zone V|
|Pacific Time||08 AM–01 PM||PST (UTC−08:00)||PDT (UTC−07:00)||Zone U|
|Mountain Time||09 AM–02 PM||MST (UTC−07:00)||MDT (UTC−06:00)||Zone T|
|Central Time||10 AM–03 PM||CST (UTC−06:00)||CDT (UTC−05:00)||Zone S|
|Eastern Time||11 AM–04 PM||EST (UTC−05:00)||EDT (UTC−04:00)||Zone R|
|Atlantic Time||12 PM–05 PM||AST (UTC–4:00)||AST (UTC–4:00)||Zone Q|
Primary U.S. Time Zones
There are four primary time zones across the contiguous United States. Some United States Minor Outlying Islands are outside the time zones. Alaska is 1 hour behind Pacific Time and Hawaii, depending upon Daylight Saving Time, is 2 hours behind. Bermuda and the Caribbean Islands, including Puerto Rico, observe Atlantic Standard Time without observing Daylight Saving Time.
Daylight Saving Time
Daylight saving time (DST) begins on the second Sunday in March and ends on the first Sunday in November. Arizona and Hawaii use standard time throughout the year. Clocks are set ahead one hour at 2 AM on the following start dates and set back one hour at 2 AM on these ending dates:
|Year||Start date||Ending date|
|2019||March 10||November 3|
|2020||March 8||November 1|
|2021||March 14||November 2|
|2022||March 13||November 6|
|2023||March 12||November 5|
|2024||March 10||November 3|
|2025||March 9||November 2|
Australia has 5 standard time zones that honor separate daylight savings times plus 2 locations (Broken Hill and Eucla) with fractional hour differences.