I've noticed that my WPC games fail to keep accurate date and time even with good, externally mounted batteries. Date/time gets out-of-whack even though settings and high scores are retained just fine. I looked into totally replacing the batteries with an NVRAM module, but apparently that wouldn't help (because, in WPC games, the NVRAM module doesn't update the real-time clock when the machine is powered off).
Is there a solution out there... a way to keep the real time clock accurate in a game like Twilight Zone, where you sorta want an accurate clock?