All 25 ‘X-Men: Days of Future Past’ Covers! Jennifer Lawrence, Fassbender and more “The ultimate X-Men ensemble fights a war for the survival of the species across two time periods in X-MEN: DAYS OF FUTURE PAST. The beloved characters from the original “X-Men” film trilogy join forces with their younger selves from “X-Men: First Class,” in an epic battle that must change the past — to save our future.”