I don't know if anyone else has noticed this continuity error, but I have. In the beginning of The Last Stand, we see Magneto and a WALKING Professor X visiting a child Jean Grey in 1986. Not only was Professor X paralyzed before that in 1961, but Jean Grey was shown to be a teenager in 1983 in X-Men: Apocalypse. One could argue that Professor X used the serum for his spine, but that's not possible, as he still had his powers and was communicating with Jean Grey telepathically. And I understand Days of Future Past fixed the timeline after 1973, but did it really change the year Jean Grey was born in?