A 5 pm reservation at Akershus? I have seen mid-afternoon (1 - 3:15 pm or so) and late evening (8 pm), but I am planning on doing the Frozen Dessert Party. TY!
It's luck of the draw. If you aren't seeing one now, you just have to keep checking for cancellations. Consider signing up for a Touring Plans reservation finder.
That's a prime dinner time and a popular restaurant so its not gonna be easy as you've already seen.
Book at your 180 days and you should be ok but if you don't then you're just gonna have to stalk it.