Did you try to reset the time?
In that Date & Time settings pane:
Turn OFF: "Set time and date automatically"
CHANGE the time to something else. Change the date, while you are there
Turn ON that same setting.
Does the time correct immediately?
I toggled everything. It didn't change immediately. However, after 10 or 15 minutes (I tried to understand what's going on during that time) it suddenly shifted to the right time.
I also found this thread. It's not exactly the same problem but I did changed the wallpaper (to the aerial wallpaper) a few days back. Maybe it has something to do with that. Maybe the time got stuck. I don't want to risk it so now I switched back to the last settings and also restarted the computer. Hope this will solve it; but it is kinda unreliable.