Well, it takes 14 billion years of our time for the external observer to witness the evolution of our universe up to this point, according to our clock. The problem then is determining at what speed the external observer's clock runs. We have no idea what the physical laws governing such an external observer would look like. There is a good chance that they would be tremendously different from those that hold here in our universe. In fact to observe our universe it would almost certainly have to exist in more than 3+1* dimensions, so that it could understand what it was observing. Since we are talking about an imaginary observer we can set its clock speed to anything we want. That of course assumes that it uses clocks. An external observer with more 3+1 dimensions might not actually have clocks as such.
*In case you aren't familiar with the designation 3+1 dimensions, that means 3 spacial dimensions and 1 time dimension, which is how we perceive our universe.
Bill Gill
