Try deselecting the box that says synchronize with Internet time.
So, is it proper now.Well, I actually had to manually goto the sync time online dialog box and press Sync now button, which used to fix the time.
But I have stopped auto sync for now.
try cleaning the cmos battery holder contacts.
and the battery surfaces.
Clean other internal parts of PC at regular intervals to avoid such problem. But careful, don't ruin it use a brush and be light on strokes.