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).

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. Arizona, Puerto Rico, Hawaii, U.S. Virgin Islands and American Samoa do not observe Daylight Saving Time. Read more about the new federal law that took effect in March 2007 which extended Daylight Saving Time by four weeks.

<Chamorro Standard Time  <Samoa Standard Time                                                     Atlantic Standard Time>  

Arizona is in the Mountain time and does not observe daylight savings time except for the Indian Navajo Area.

The four time zones of the 48 contiguous United States (boundaries are indicated by the red line).
County boundaries are shown in grey and state boundaries are dark blue.

Indiana and Arizona are special cases. Most of Indiana is in the Eastern Time Zone but does not utilize Daylight Saving Time.  Arizona, while it is in the Mountain Time Zone, does not utilize Daylight Saving Time.

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