<P> Daylight saving time in the United States is the practice of setting the clock forward by one hour during the warmer part of the year , so that evenings have more daylight and mornings have less . Most areas of the United States observe daylight saving time ( DST ) , the exceptions being Arizona ( except for the Navajo , who do observe daylight saving time on tribal lands ) , Hawaii , and the overseas territories of American Samoa , Guam , the Northern Mariana Islands , Puerto Rico , and the United States Virgin Islands . The Uniform Time Act of 1966 established the system of uniform Daylight Saving Time throughout the US . </P>
what states do not allow daylight savings time
Arizona Navajo