When I first got my HoMedics SS-4510 alarm clock I set it 20 minutes ahead of time soI could be on time. Now a couple of years laster I don't need the extra 20 minutes but I cannot figure out how to set it back to real time like it I did manually. I unplugged the unit and adjusted the time zone, but it still is 20 minutes ahead of time. Can you please help me figure this out? Thank you...