been a while since I did this but..............boot machine. while it's booting keep tapping the delete key. the BIOS should eventually appear. I think the first screen that comes up will have the time on it. you'll need to use your arrow keys and the plus+ and minus- keys to change the time........ i think.
if you didn't make it into the bios......... reboot and start tapping delete key sooner.
after you make the changes to time - and date if need be......... hit the F10 key and enter key to save. machine will reboot. let it. when at desktop check the time in lower right corner.