Under the Uniform Time Act, as amended, States may exempt themselves from observing Daylight Saving Time by State law. If a State chooses to observe Daylight Saving Time, it must begin and end on federally mandated dates.
daylight saving time
Under Federal law, there are two ways in which an area in the United States can be moved from one time zone to another.
The U.S. Department of Transportation (DOT) oversees the Nation's time zones and the uniform observance of Daylight Saving Time. The oversight of time zones was assigned to DOT because time standards were first instituted by the railroad industry.