DIC Displays Wrong Day and Date

The first thing I would do it check the battery and the cable connections because if the system loses power or if the voltage goes below 10 volts even for a second it will cause this issue.

https://www.2carpros.com/articles/car-battery-load-test

and

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

does this vehicle have a factory CD 6 disc changer?if it does its a software issue in the radio,the radio needs to be replaced and reprogrammed if the vehicle was built before jan 6 2004,if it was built after this date it has the software and may just need to have the radio replaced.

Couple of things, does the vehicle have PCJ premium sound system?The 6 disc changer should be part of the radio, which means you can load 6 CD's into the radio at once, plus your vehicle was built before january 6 2004 so you might have to updat the radio with updated software. The radio, DIC and IPC are all connected. As far as fixing it without replacing the radio, you really cant, replacing the radio is the only way. If you replace it, you should go with a factory one because it will work with your vehicle and function the wright way, but the down side is the OEM radios cost WAY to much money. You could go aftermarket which is cheaper but more of a headache and might cause other problems.I would possibley call the dealer and explain what happened they might be able to help. As far a scrolling throught it I cant answer that I dont work on many G-prix's just chevrolet. Post back with how you make out.