The United States mainly uses six standard time zones（标准时区）. From east towest they are Eastern Standard Time (EST), Central Standard Time (CST),Mountain Standard Time (MST), Pacific Standard Time (PST), Alaskan Standard Time (AKST), and Hawaii-Aleutian Standard Time (HST).

Besides, Atlantic Standard Time (AST), Samoa standard time (UTC-11) and Chamorro Standard Time(UTC+10) are correspondingly adopted in oversea territories.

Daylight Saving Time（夏令时） 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 alongwith Daylight Saving Time. Eastern Standard Time (EST) becomes Eastern DaylightTime (EDT), and so forth.