After 12 films and almost 20 years, the X-Men franchise comes to a close with Dark Phoenix, a storyline which has already been told in a previous installment, 2006's X-Men: The Last Stand. That this is the Phoenix Force's second go-around underscores a sometimes confounding lack of continuity from one film in this series to another — if you aren't looking carefully.

Dark Phoenix writer-director Simon Kinberg, who has worked on every X-Men film since The Last Stand, including all of the Wolverine and Deadpool spinoffs, tells SYFY WIRE that the filmmakers have worked hard to create a coherent and cohesive timeline that makes sense.

"I think it does matter," says Kinberg. "Obviously the timeline is different with regards to some of the offshoots like the Wolverine standalone movies and Deadpool. But in the mainline X-Men movies, I have had in my mind, and in my office, and in my computer, a continuity that I've tried really hard to keep to."

Credit: 20th Century Fox

Kinberg acknowledges that the events of the first three films in the series don't sync up with the stories told starting with X-Men: First Class — which is why Dark Phoenix isn't designed to bring the franchise's mythology full circle even as it wraps the series for the Fox era.

"The original films don't really take over a cyclical timeline," he says. "Not to get too geeky about it, but because we reset the timeline at the end of Days Of Future Past, it essentially erased X-Men 1, 2, and 3 from the continuity of the timeline, because anything that would have happened after 1973, which is when the past part of Days Of Future Past happens, would have happened differently than it was portrayed in those movies."

Kinberg offered a few examples of what that means, practically speaking.

"That's why when Wolverine comes back to the house at the very end of the movie, Famke Janssen (Jean Grey) and James Marsden (Cyclops) can still be alive, because that didn't happen," he continued. "So again, not to get too geeky and it can start to pretzel your mind. But it's not as though the end of my Dark Phoenix movie is the beginning of X-Men 1."

In fact, Kinberg said that the myriad complications that were outwardly created by plots involving time travel in Days of Future Past actually resolved issues that popped up in the continuity of the franchise as a whole. "Days of Future Past helped reset the timeline so that Apocalypse and Dark Phoenix could exist by their own rules, so to speak."

Credit: 20th Century Fox

Among the many questions that still remain unanswered about choices made in the series, the biggest one that lingers is precisely how characters who are in their teenage years and twenties in 1962 during the events of First Class can remain so youthful and vivacious by the time of Dark Phoenix, where at best they look five or ten but certainly not 30 years older.

"Well, Jennifer [Lawrence] is the easiest one to rationalize because she can make herself look however she wants to make herself look," explains Kinberg. "The aging on her is Mystique should actually always be the same age when she's blue. And when she's white, she is just pretending to look young, the same way she was pretending to look like Richard Nixon."

"But for all the other characters, Michael Fassbender, James McAvoy, Nicholas Hoult, going back to First Class, they certainly have not aged 30 years since we started making those movies 10 years ago," he acknowledges. "And the way that we sort of rationalized it, and it is a rationalization for sure, was that they aged a little differently because they're mutants, and we hoped that the audience would go with that. And so far that's not been a problem for the audience."