The United States uses seven 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 (AST), and Hawaii-Aleutian Standard Time (HST).

Daylight Saving Time begins at 2:00 a.m. local time on the first Sunday in April. On the last Sunday in October 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. Arizona, parts of Indiana, Puerto Rico, Hawaii, U.S. Virgin Islands and American Samoa do not observe Daylight Saving Time.