I bought a big clock for my kitchen. Think public school/ DMV size. It runs on 110 volts AC plugged into an outlet behind the clock. It was advertised as self-changing when DST starts and ends. But I had to set the initial time the normal way with a little wheel in back. Last night it changed to Standard Time all by itself!!! How did it do that?!? It is not wired to anything but my house current. I don't have WiFi.