Get it checked at the closest service point of the manufacturer.
Changing the CMOS cell in a laptop is way more complicated than for a desktop, if you are new with complex rigs, small screws and tiny wires, I'd suggest get it checked and don't try it yourself.
If you are well versed with the complexities of small screws and components then you can download the layout diagram for the Aspire 8920G from the net and go through it, then change the CMOS cell on the mobo of the laptop and you shouldn't have the date time problem.
Another problem could be an electrical short that could be caused every time you plug in the power cord.... another technical matter.
IMO : get it checked.
When i plug my power core into the laptop socket my blue light will flash and the laptop itself won't charge properly.
Im wondering if my laptop simply needs a new battery or if the point where i connect my charger is broken.
Also my date and time is contastnly wrong despite resetting it right. Any ideas?
Using AC adapter all the time will kill be battery slow. Battery are supposed to be fully charged and fully discharged. If you plan to use AC adapter all the time, remove the battery. You can do a cisual check on the connection to see if it is broken. Broken connection is considered by manufacturer as physical damage and not covered by regular warranty. Another possibility is bad AC adapter so try different one.
As for the date/time issue, most likely the CMOS coin cell battery needs to be replaced. My advice is to take to an authorized computer service place to replace it.
Don't know about date/time but,I just had Battery charging trouble with an Acer Aspire..what I did was,go into device manager and click 'batteries' right click compliant control method battery and DISABLE.then power down..remove battery and boot up again,then go back into device manager ..click batteries..and Enable.power down once again insert your battery and it should work.although I had to do this twice.hope this works for you.