I know it's probably been said already, but it's time to officially discuss this
The prologue to X-Men: First Class takes place in 1944, where Charles is a young boy. If the sources that say he was born in 1932 are right, he'd be 12.
Then the main events of First Class take place in 1962, 18 years after the prologue.
Then Days of Future Past takes places in 1973, 11 years later.
Then Apocalypse takes place in 1983, 10 years later.
Then, Dark Phoenix takes place in 1992, 9 years later.
That's 30 years between First Class and Dark Phoenix, making Charles about 60, the same age as Patrick Stewart was when the first X-Men was filmed.
So, while James McAvoy is 40 now, that's still 20 years younger than Charles is in Dark Phoenix. 10 years could be overlooked, but not 20 years when Charles should be Patrick Stewart's age now.
Same goes for Michael Fassbender as Magneto instead of Ian McKellen. If they wanted to keep using them, they should've set it like a year after Apocalypse.
If anyone can come up with an explanation for this, let me know, coz I think this movie sounds interesting. Of course, Jean's probably gonna die, despite the fact that she appeared in the good future of Days of Future Past, coz they can never stay consistent.