A leaked casting sheet that surfaced on ComicBookMovie appears to confirm that the Bryan Singer-helmed follow-up will be set primarily in 1973.
X-Men: Days of Future Past sees the X-Men travelling in time to change a major historical event that could globally impact on man and mutant kind.
Original trilogy stars Patrick Stewart, Ian McKellen and Hugh Jackman are among the actors expected to reprise their roles, alongside X-Men: First Class members James McAvoy, Michael Fassbender and Jennifer Lawrence.
Singer took up the director's chair after X-Men: First Class helmer Matthew Vaughn dropped out of the project due to scheduling conflicts.
X-Men: Days of the Future Past is planned for a July 18, 2014 theatrical release in the US and UK.
Watch Michael Fassbender discussing the sequel with Digital Spy below: