Prior to its passing, numerous citizen groups in Arizona sent in petitions for the state to be exempted from this and Arizona Governor Jack Williams also supported exemption. Arizona farmers were especially against it because they were often up early in the mornings when temps are cooler (A note regarding the poster above - after cooling off during the night, it is morning when you get both cool temps and daylight NOT evening).
An editorial in the Arizona Repubic newspaper at the time summed up the reasoning of many Arizona citizens :
"...we must wait until about 9 p.m. to start any night-time activity such as drive-in movies, moonlight rides, convincing little children it’s bedtime, etc. And it’s still hot as blazes!"
On the basis of the petitions and the pressure from Arizona politicians, the Nixon adminstration (through Transportation Secretary Claude Brinegar) granted that Arizona (as well as Hawaii and several other territories) be exempted from the law and it has been that way ever since.