[HartleyMBaldwin]

It is up to the states.

Then why even bother with a national law?

[Dilbert San Diego]

I think there’s a national law because time zones are set at the federal level. Then within such federal regulations, states can decide about daylight time. That’s my understanding anyway.

Then the next question would be, can states decide on their own to have their own time zones. I don’t know the answer to that.