On the set of the next X-Men film, several actors have been seen dressed 70s style. This is due to the fact the X-Men First Class timeline will be set in the 70s. While the post-X-Men: The Last Stand timeline is much later in Days of Future Past. Yes... if you've been living under a rock, there are going to be two timelines in this movie.
Check out the stylish duds worn by Magneto, Professor X and whoever actor Peter Dinklage is playing (it's gotta be Trask, right?)