Hyundai Repair: car clock 2005 sonata, low battery, right time

Question
what is wrong with my clock on the dash? it wont keep right time. everytime i restart my car it changes and sometimes it wont come on?

Answer
Every instance I've seen where the clock won't come on when the engine is running has been caused by a problem in the clock itself.  

A low battery, however, can cause the clock to run slow, and if low enough, can cause the clock to lose its memory when the engine is started because the voltage lowers too far.