To change the CMOS battery, the laptop would require servicing.
Turn off your laptop, unplug all wires, remove the battery, and hold the power button for thirty seconds. Afterwards, reattach the battery and connections.
If that doesn't fix it, you may want to consider a recovery? Recovering your laptop to its original, out-of-the-box state is a great way to eliminate software as a possible cause of the problem. Note that doing a system recovery will return the laptop to its default conditions, completely wiping your data. Information on how to perform a system recovery can be found in your user's guide. On most models, you can hold '0' (zero) while booting to initiate the procedure.