I agree that one shouldn't have to keep the D80 powered on to charge the clock battery. But then what am I to conclude from the fact that the clock battery appeared dead and each time I changed the main battery the clock defaulted to 2006? This has been the case for some time. But when I left the camera powered on for 2 days, that procedure appeared to finally charge the internal battery again. Yes, page 103 of the manual does state that 2 days of charging should power the internal clock for about a month, but how does that occur if not by keeping the camera powered on? It certainly wasn't happening with the camera powered off.
Perhaps I'm not understanding something pretty basic here.
Many thanks if you have the answer to this conundrum.