<P> Five states are fully contained in the Mountain Time Zone: </P> <Ul> <Li> Colorado </Li> <Li> Montana </Li> <Li> New Mexico </Li> <Li> Utah </Li> <Li> Wyoming </Li> </Ul> <P> Four states are split between the Mountain Time Zone and the Pacific Time Zone . The following locations observe Mountain Time: </P> <Ul> <Li> Arizona--though fully in the Mountain Time Zone, clocks are essentially on the same time as Pacific Daylight Time in the summer . The Navajo Nation, however, does observe Daylight Saving Time, and its clocks are aligned with Mountain Daylight Time in the summer . </Li> <Li> Idaho--Southern Idaho </Li> <Li> Nevada--West Wendover is officially on Mountain Time; Mountain City, Owyhee, Jackpot, and Jarbidge observe Mountain Time unofficially </Li> <Li> Oregon--the majority of Malheur County </Li> </Ul>

Where does the time zone change from mountain to pacific