Date photos

Hi there my Name is Pauline and I am from a volunteer fire service in New Zealand, we have on our trucks two of your cameras, they are both Pentax Optios5n I hope thats right, I would like to know if you could tell me how I can get the dates on the photos either on the front or back, as this would make my job of archiving alot easier, I have tried to find in the manual, but have had no luck and thought I would let my fingers do the walking. I look forward to hearing from you, hope you can help thanks regards Pauline