If they start seating at 8am, you might not. Akershus sits in groups. Usually they will not allow you to check in earlier than about 5 minutes before your ADR time. And they generally take a group in at a time. I think they kind of do this at a lot of the buffets but I have noticed it the most at Akershus.
However, that being said, with an early ADR, you may get lucky because you are not waiting on a restaurant of other people to be done eating. I do know we showed up with only 3 of the 4 of us one time because Tyler left something in the room so ran back and met us there (he wasn't far behind but had to grab the next bus) and the were fine with it and we got seated as soon as he reached us...and it was Christmas day too.