I recently made this code modification for an Airsoft team in Russia. It uses a 24-hour clock instead of the 12-hour clock with PM indicator. After detonation of the device, the clock simply continues to read 00:00 until the DET button is pressed again. Then the clock time is displayed again.
The code can be downloaded from here: http://nootropicdesign.com/defusableclock/downloads/DefusableClock10.zip