Infuriating fact if you have to deal with historical time stuff: in the U.S., it used to be that not only could each city decide whether or not it observed DST,

Infuriating fact if you have to deal with historical time stuff: in the U.S., it used to be that not only could each city decide whether or not it observed DST, it could also decide on its own when DST began and ended. It was this way until 1966, at which point a law was passed to make it uniform, and the duty to enforce it fell on the Department of Transportation.