The more Deadpool timextravel, the harder it gets.Just watched Dark Phoenix and was trying to puzzle out the X-Men timeline as a mental exercise (I'm aware that it makes no sense). I think that if you take the films in release order, there's just a tiny thread to grasp that makes some kind of continuity possible:
X-Men First Class-->Origins: Wolverine-->X-Men-->X2--X-Men: Last Stand-->The Wolverine-->Days of Future Past (Future)
Between 1962 and 1986 in this timeline, Charles has some kind of serum that allows him to walk by 1973 as seen in Days of Future Past, explaining his mobility in Origins: Wolverine and X-Men: Last Stand. Some version of the 1983 events of Apocalypse also take place, explaining the references to Charles and Erik (re)building Cerebro in X-Men and their working together as late as 1986 in Last Stand. Mutants are hunted by Trask robots in 2023.
Days of Future Past Timeline
X-Men First Class-->Days of Future Past-->Apocalypse-->Deadpool-->Logan-->Deadpool 2 (Cable future)
Logan travels back in time to 1973, disrupting the timeline. Some version of the Statue of Liberty battle in X-Men may have still occurred, as per Logan. Although no new mutants are born from 2009 forward, Xavier continues to operate his school, with Scott Summers alive and Jean Grey still in human form, into 2023. By 2029, Xavier and Logan have both been killed. At some point after this, the world is in a post apocalyptic state with Firefist and Cable being two of the only remaining mutants.
Deadpool 2 Timeline
X-Men First Class-->Days of Future Past-->Apocalypse-->Deadpool-->Deadpool 2 (present)
Cable travels back in time to 2018, disrupting the timeline. By this point, Xavier is still in charge of his school. Deadpool gains access to Cable's time travel device, and begins disrupting the timeline further.
Deadpool 2 Timeline (altered)
X-Men First Class-->Days of Future Past-->Apocalypse-->Deadpool-->Deadpool 2 (Saving Vanessa, saving Peter)
Deadpool travels back in time to save Vanessa, then travels forward in time to save Peter, changing the timeline. Some version of Deadpool 2 still takes place.
Deadpool 2 Timeline (altered again)
X-Men First Class-->Days of Future Past: Rogue Cut (why not?)-->Apocalypse--->Days of Future Past: Rogue Cut (Future)
Deadpool travels back in time to kill Ryan Reynolds in 2010, changing the timeline. Some version of Deadpool 1 and 2 takes place (probably). And what the heck, let's throw the Days of Future Past: Rogue cut in here for the hell of it.
Deadpool 2 Dark Phoenix Spoilers Timeline (altered again again)
Deadpool 2 (Hitler Baby Deleted Scene)-->Deadpool 2 (Wolverine credits scene)-->X-Men: Dark Phoenix-->New Mutants (?)
Deadpool travels back in time to 1889 to kill baby Hitler, but finds he doesn't have the stuff to do it. Nevertheless, he's altered the timeline, restoring some version of the 1979 Deadpool. He travels forward to clean up the timeline by killing his past-future-past self. First Class, Days of Future Past (1973 version), Apocalypse all occur more or less as they originally did, though Jean may have been born earlier.
In 1992, Raven dies, Jean ascends into a Phoenix form, the school is renamed in her honor, Charles retires. This is the current status quo of the X-Men until New Mutants comes out. (I'm just gonna guess that Deadpool messing with the timeline also caused the re-shoots to be delayed.)
Nope, still makes no sense. Oh well, I tried. XD