I'm wanting to say it started around WWII to save energy, then they stopped it, then it started again around the energy crisis of the 70's.
It's BS regardless. I could see during WWII when everybody was using incandescencent lighting yet, but with CFL's, regular fluorescents, HID, and LED's I can't see it saving enough to justify the energy required to change every clock in the house twice a year.
From a farmers perspective it's still BS. We have x number of hours per day of daylight regardless of what the clock says. In my case daylight savings even costs local business money. During hay season I don't get done till dark, wit hit getting dark an hour later, by time I shower, put on clean clothes and get ready to leave, all the local places that serve food are closed. Used to be able to get a late night dinner when it got dark an hour earlier.