Could be, but give it a chance to heal (recharge). I was sure the PRAM battery was hosed on the PBG3 Firewire I just bought, but then I pulled the dead main battery to do some surgical inspection inside it. With the main battery out and the 0% charge symbol replaced by the little AC plug symbol, the PRAM battery slowly recovered to respectable capability. I was getting the bad date message also, but no longer. But don't sleep the thing with the AC disconnected because even fully charged it is just minutes until the PRAM battery has given its all trying to support main memory. Without a main battery, it is probably best to shut down when not using but leave it plugged in to the powered AC adapter.

See for example

http://docs.info.apple.com/article.html?artnum=30580

http://docs.info.apple.com/article.html?artnum=106216

http://support.apple.com/kb/HT2295?viewlocale=en_US

http://docs.info.apple.com/article.html?artnum=58401

http://support.apple.com/kb/HT2287?viewlocale=en_US

but do not be surprised if you find some contradictions even within the Apple documents. Once you are in the support areas do a search on PowerBook G3 and you will see all kinds of tidbits about your Lombard and related PowerBooks.