I know I'm 3 years late to this particular party but I just re-watched the movie and so this post....Well I looked it up on the following website: www.moonpage.com and on the 11/11/3978 which is the chronometer reading on the spaceship, the Moon will be approximately 4.5% full. Now taking into account dialogue in the film that it took them several days to traverse the Forbidden Zone the Moon's phase was approximately 1.25% full with it being a New Moon on 13/11/3978 at approximately 10:45am est. Don't know if any of that helps.
You really approached this from a scientific perspective??!!
Lol!!!