Board Thread:Ask Questions/@comment-29253708-20170316165413/@comment-27575896-20170316174652

Currently, only two or three tates don't use it, like Arizona, Alaska, and maybe something else.

DST (hey, that's your called nickname!), or Daylight Savings Time, is used to help people "get more done during the evenings, as you have more light". More info found here: http://www.webexhibits.org/daylightsaving/c.html

Not a very good reason, but for once it was a PUBLIC decision.