<human>:  Where does the title of the movie, ‘X-Men: Days of Future Past’ come from?
<bot>: The title comes from the comic book series, Days of Future Past. It is a story about a dystopian future where mutants are hunted down and exterminated. The comic book is set in a future where mutants are the minority and are persecuted and feared. In the comic, the mutant characters travel back in time to prevent their own futures from happening. The comic book series is set in the Marvel Universe.