WARNING: The following article contains major spoilers for Dark Phoenix, in theaters now.
Following the end of the original trilogy, the timeline of Fox's X-Men films quickly got complicated, making it somewhat difficult for fans to follow. Ignoring the fact Erik Lehnsherr and Charles Xavier are surprisingly spry for two people entering their golden years, Dark Phoenix introduces numerous issues to the timeline after X-Men: Days of Future Past did its best to correct problems previous entries in the series introduced. There are far too many issues to explore here, so we're just going to focus on the major ones now by laying the X-Men timeline out plainly.
In the world of Fox's X-Men, everything prior to 1972 presumably remains the same. That means Logan's story in X-Men Origins: Wolverine follows the same path up until his involvement in the Weapon X Program. He still murders his family in 1845, runs away with Victor Creed and becomes a soldier who fights in several wars, including World War II. Several thousand miles away in Nazi-occupied Poland, Erik Lehnsherr discovers his mutants powers for the first time and loses his mother to Sebastian Shaw's sick experiments in 1944, while, across the Atlantic, Charles Xavier and Mystique meet for the first time at Xavier's mansion in Westchester, New York.
During the 1950s, everyone is just doing a bit of growing up. Erik has a short-lived relationship that results in the birth of his son, Peter Maximoff. The events of X-Men: First Class occur in 1962. The X-Men are formed as part of a CIA defense project, the Cuban Missile Crisis occurs and Erik, Mystique and Charles eventually go their separate ways. Later in the decade, Lehnsherr is accused of assassinating President John F. Kennedy.
During the 1970s, Mystique assassinates Bolivar Trask and the Vietnam War escalates. Wolverine and Victor Creed are recruited into Division X by William Stryker, but the former abandons the team several months later. A few years down the line, he's drawn back in by Creed's apparent rampage and willingly participates in the Weapon X program. During this time, Cyclops and a group of young mutants from a Weapon X facility on Three Mile Island are taken in by Charles Xavier.
In the decade that follows, Xavier and Magneto (somehow) jointly recruit a young Jean Grey. After that, Erik and Charles presumably go their separate ways again, leading to the events of the original X-Men trilogy that began in 2000 and led to the future world of X-Men: Days of Future Past. That film rewrote the timeline, beginning in the 1970s. It worked almost perfectly. At least, it would have were it not for the films that followed.
At the end of Days of Future Past, Logan finds himself in the year 2023,with the X-Mansion full of his old friends and allies. Professor X, Cyclops, Storm, Beast, Iceman, Rogue and Jean Grey. It's a happy ending for the film -- until you get to the events of Logan -- but this becomes somewhat problematic with Dark Phoenix.
In the new timeline, Wolverine somehow finds himself serving as a bodyguard to a rich man's daughter. Instead of living out his life as he would and serving in the Vietnam War with Victor, Logan actively searches for Charles and Erik, leading to the creation of an alternate timeline. This time around, Wolverine is still captured by William Stryker, or rather, Mystique disguised as Stryker (for reasons that have never been explained), and he still ends up in the Weapon X facility, where we see him in the 1980s in X-Men: Apocalypse, when Cyclops, Nightcrawler and Jean encounter him.
The world comes close to complete destruction, but the X-Men save them all with a lot of help from Jean, who destroys En Sabah Nur by unleashing her power. The world took notice and the X-Men become world famous. Then the events of Dark Phoenix happen: The X-Men travel into space for a rescue mission, Jean absorbs a mysterious cosmic force and in the end sacrifices herself to save the world from alien invaders. Xavier retires, Hank becomes headmaster and the rest of the X-Men live... ever after.
Dark Phoenix's ending doesn't reflect that of Days of Future Past at all. If fans are left to fill in the blanks on their own, then the end of Dark Phoenix is sure to be rendered wholly meaningless, because we'd have to assume that Jean returns from the grave, like a Phoenix, and that Xavier comes back from retirement causing Hank to step down as headmaster. This would all be acceptable if not for the fact that this was the last X-Men film in the franchise. The story is over now and we're left to try to put the pieces together. We can try, but it can't really be done.
We haven't even mentioned some of the other gnawing details that X-Men: Apocalypse and Dark Phoenix introduced. Like the fact that some characters appear far earlier than they should have. To name a few examples, Cyclops is a lot older than he was in the original timeline, as is Warren Worthington, who only appeared in X-Men: Apocalypse, which was set in the 1980s. Just for reference, Warren appeared as a little boy in the 1990s at the beginning of X-Men: The Last Stand. As if that wasn't enough, characters tend to meet and evidently forget that they ever knew each other. Case and point: Wolverine and Sabretooth between the events of X-Men Origins and X-Men. Mystique is also now dead, despite her role in the original X-Men franchise.
Little things like these marred the X-Men franchise's potential as a storytelling titan. Even introducing an alternate timeline wasn't enough to fix these gaping holes. If we look at the franchise as a whole, it's somewhat fitting that Dark Phoenix should end the series with one last confusing quandary.
Written and directed by Simon Kinberg, Dark Phoenix stars James McAvoy, Michael Fassbender, Jennifer Lawrence, Nicholas Hoult, Sophie Turner, Tye Sheridan, Alexandra Shipp, Kodi Smit-McPhee, Evan Peters and Jessica Chastain.