The time syncs with onstar cellular network, if it's anything like volt. So if you're travelling and hit a cell tower with incorrect time, it may sync to that time and sync back when it hits one with the correct time.
They added time sync and text messages in 2014, both of which you're missing out on.My volt has never changed its time by itself. Whenever we do the daylight savings time switch, I've always had to manually increase of decrease the hour. I wish it did use the on-board cellular phone to sync the time. Or at a minimum, song the time from a smartphone plugged into USB or Bluetooth.