Problems with starting up my laptop

Hello, My Dell laptop has erratic start up issues. Most of the time when I power up my laptop I only see a black screen and I can hear fan and see power lights on. After a few times of powering off and on the computer finally comes up with an error showing that time and date are set incorrectly and prompts me to press f5 to run a diagnostic. I do so then I press escape to boot up. Once computer goes to desktop I have to set my time and date because everytime pc boots up it show date of November 2007. Can you tell me what I need to do to fix this problem. My pc seems to work great after once it is powered up and running. I really appreciate the help.