Date and Time always needs re-setting

Everytime I open the battery compartment to take out the chip to place in my computer, I need to re-set the time and date.  I think this is a new development, since I have been removing the chip prior to this and never had to re-set the time.  The camera is about 1 1/2 years old.  Does anyone know if there is anything I can do to repair this, or is the memory messed up.  It still takes photos and works well besides this problem.