My 920 had a sticker on the back with a manufacture date. Not sure that date will indicate anything about the date of the battery. I am sending mine to ATS so I don't have a problem.
I think the date is in the serial number. Just can't remember which number it is. Someone is bound to help. I have changed a battery on a 920 and a VCII. There are also instructions in the forums for that as well. I got the batteries from Mouser in Texas but you can also get them at Radio Shack. Good Luck.