Press F10(repeatedly) as your laptop is turning on.
The bios screen will come up.
Look for "settings"
Set date and time.
All set.
If the error message comes up again. You will need to replace your laptop battery. Take it to a computer shop. Or HP.
As an alternative, you can try to go into windows and have it set the date and time. Click on the Date/Time on the start bar, set the date/time to what it needs to and restart the computer.