The WPC clock runs slow, or the game boots with "Set Time and Date". On Twilight Zone the clock mode uses this time.

Game clock loses time or asks to set the time and date

Cause: Weak batteries, or corroded holder contacts lowering the voltage at U8.

Checks

• Measure the batteries and the voltage at U8.

Fix

• Fit new batteries; if it persists, replace the holder.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• New batteries die in weeks or settings still lost: U8 RAM
• Fitting a remote battery holder to a WPC CPU board
• Switch matrix row fails with good switches and diodes: battery-damaged CPU board
• Coin door Begin Test button does nothing: acid-broken trace on the CPU board
• "Factory Setting" or "Adjustment Failure" at power-on
• Settings lost because battery voltage at the RAM is too low
• "Factory Settings Restored" every power-on
• "Factory Settings Restored" at power-on

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)