Although I'm not an expert on the mechanics, this is kinda interesting topic, in a watch-geeky way. I could not find a picture with the dial side mechanism exposed, but it looks like there are a total of four disks - two for day and two for night. Notwithstanding what the particular implementation may be here, I think that in general it should be possible to have the sunrise/sunset display show 100% day or 100% night. What I feel may be the issue though is the way the sunrise/sunset indication works. The indication is 'continuously' driven by a cam, and even if having the indication reach the extreme position of 100% day (effectively no sunset) or 100% night (no sunrise) was no issue, having it 'stay' there for a (varying) amount of time/days could be. Perhaps the cam could be fashioned in a way that made this possible - not sure. But even if this was the case, I'm pretty sure there would need to be a separately manufactured cam for each location. Using a single cam that is adjustable to different locations without requiring a change of parts, which is kind of the point of this 'Anywhere', seems (to an amateur like me anyway!) just too difficult to achieve, if any and all latitudes are allowed without restriction.