clock problem
 

i just purchased a 2003 Toyora Camry XLE and i have a problem. I set the time at 12:30pm and went inside my house and came back to the car 2 hours later and the time was still 12:30pm. So i notice once the car is turned off the clock does not move forward it only works when the car is on. This is a very weird issue and i dont know where to begin. Its like the clock doesnt tick when the car is off...anyone help?