"God, when did Wolverine become the reasonable one? These X-Men get crazier every year." 
 Yes, they certainly do, and this 10-part crossover that was part of the 50th anniversary of the original title proves Maria Hill's point. 
 Since the X-Men and time traveling go together like the Doctor and Clara, then I guess it's only natural that this would lean heavily on that concept, especially since the All New X-Men are actually the original team brought forward in time due to a very curious decision by the present day version of Hank McCoy. Even though almost everyone agrees that having them remain is a spectacularly bad idea, they just keep hanging around until a future version of the X-Men show up demanding that they be returned immediately to prevent some horrible outcome. 
 This is a fairly entertaining story, and it does at least try to address the elephant in the room regarding the original X-Men: if everyone except young Jean Grey thinks that having them stay actually endangers the entire space-time continuum as they know it, then why haven't they been sent back? The problems start popping up because of the whole superhero vs. superhero thing which is an angle that Marvel has leaned on far too heavily since the Civil War storyline. 
 So all the battles here take place between past X-Men, present day X-Men, future X-Men, ex-X-Men, and future ex-X-Men. Oh, and SHIELD, too, because you might as well have the worldwide peacekeeping force and the good guys at each other's throats while you're at it. *sigh* Remember the days when superheroes fought supervillains in comic books? 
 This causes several problems with characters and story because to generate conflict some of the present day X-Men have to decide that letting the past X-Men stay in place is a good idea even when they barely avoid a very scary incident at the beginning of the story that shows them how the timeline can be disrupted just by their presence. (view spoiler)[I just don't buy that Kitty Pryde and Rachel Grey would think that they should let the younger X-Men stay with so much at stake, and I certainly don't believe that Kitty would jump ship to crazy Scott Summer's renegade band of mutants over it. (hide spoiler)] 
 This puts the reader in the position of having to root that the people endangering all of time and space to win when there's no good reason presented why they should. (view spoiler)[ I guess you could argue that since the future Brotherhood is posing as the future X-Men want to send them back that it shows that Kitty, Rachel and the younger X-Men are right, but we're never told why. (hide spoiler)] A lot of this could be avoided if it had been written that a villain had brought the original X-Men forward in time for some nefarious scheme, and that they were stranded in the present . Then we could still have the good story of the originals dealing with the present day stuff, but it wouldn't feel like they were recklessly endangering all of existence in doing so. 
 Even worse is that despite all of this timey-wimey stuff none of this really gets resolved which is typical for one of these big crossover events, but it makes reading a big 10 part story arc seem kinda pointless despite a generally compelling story.