Can not re set time
Are you trying to reset the timer or the Clock? It's a bit different on each stove, but usually if it's the clock, you press the Clock button TWICE, the time will then begin to flash on and off. then press the + or - sign to increase or decrease the time. When you have gotten to the time you desire, PRESS the Clock button ONCE more. The time will be set, & then you should be all set :).
If it's the KITCHEN TIMER, Press the Kitchen Timer button ONCE, the timer will start flashing. It will usually flash all 0000's. Press the + sign to add minutes, then Press the Timer Button ONCE again, it will be set to the amount of time you added and will beep once the time runs out.
Disclaimer: This instruction is primarily for the General Electric Stove. If you state your specific model, I could be more specific.