Odometer went from miles to kilometers on 2003 Chevrolet Monte Carlo

I parked the car in the garage on friday, started it up on sunday and realized everthing went metric even the thermometer reads in celcius

Asked by for the 2003 Chevrolet Monte Carlo
In your owner's manual there will be instructions that explain how to re-set the car from metric to standard. As to why it did it, possibly your battery is getting old. How old is it? Or worse if it keeps happening, then that may mean that the instrument panel is wearing out, which can happen on some GM cars.