Days of Future Past is the name of a popular storyline in the Marvel Comics comic book The Uncanny X-Men issues #141 an #142, published in 1981. It deals with a dystopian alternate future in which mutants are incarcerated in concentration camps. An older Kitty Pryde transfers her mind into the younger, present-day Kitty Pryde, who brings the X-Men to prevent a fatal moment in history which triggers anti-mutant hysteria.