I've looked into this, here's how it's done.
According to the law, any governor can exempt their state from daylight saving. They meet for an annual convention twice a year. At that meeting, all the governors can exempt their state at once by submitting a letter - I think to congress? Or (time.gov), that crazy dept.
It could be done thorugh normal means but getting rid of Daylight Saving Time would end up packed with pork like funding some wars and shit.
this is the best way.