Since there seems to be so many questions regarding the continuity and time lines of the X-Men movie universe now that Days of Future Past is out, I thought I'd put together a handy Q&A to help people out. This will of course contain massive SPOILERS for all the X-Men movies, you've been warned. FOX put out a cool 25 Moments viral site to help with some of the dates, which can be seen here
http://www.25moments.com/
Let's start with the time lines and break them down by what movies fit into where.
We'll call them X-A and X-B
All that follows happens in both the X-A and X-B time lines...
En Sabah Nur (aka Apocalypse) is seen building the great pyramids with his Four Horsemen watching on the horizon (DoFP)
James Howlett (aka Logan aka Wolverine) born in 1835 in Canada (Origins)
James and his half brother, Victor Creed run away from home in 1845 (Origins)
James and Victor live on the run and fight in the Civil War, WW1, and WW2 (Origins)
Xavier (age 12) meets Raven (age 10) in 1944 (FC)
Erik is separated from his family in Poland during the Nazi invasion and meets Sebastian Shaw in 1944 (FC)
Logan saves a Japanese officer named Yashida during the atomic bombing of Nagasaki in 1945 (TW)
Charles meets Moira MacTaggert in 1962 (FC)
Charles (now age 30) and Erik (around age 30, slightly older) meet for the first time in 1962 when Erik tries to kill Shaw and Emma Frost aboard their boat (FC)
Charles, Raven, and Erik meet Hank McCoy (around age 25) (FC)
Hank shows Charles and Erik a prototype of Cerebro (FC)
Charles uses Cerebro to help find other mutants to recruit and train them (FC)
Charles and Erik go on a recruiting mission and are able to recruit Angel, Darwin, Banshee, and Havok (FC)
Shaw shows up with Azazel and Riptide to sway the young mutants while Charles and Erik are away. During this confrontation, Darwin is killed and Angel leaves with Shaw. (FC)
The Cuban Missile Crisis plays out as Shaw's team and the X-Men fight one another. Erik kills Shaw and paralyzes Charles with an errant bullet. (FC)
Erik, now calling himself Magneto, leaves with Angel, Azazel, Riptide, and Raven (now going by Mystique). They then free Emma from her prison. (FC)
11 years pass. During this time, Magneto is blamed for the assassination of John F. Kennedy in 1963 and locked away in an underground concrete prison designed by Trask Industries under the Pentagon in 1964. Mutants are still not publicly known and those that are are killed or captured for use in experiments. Among the dead, Azazel, Tempest, Angel, and Emma Frost. Xavier officially opens the Xavier Institute in 1965 (http://www.25moments.com/#!/moments/1965).
http://www.thebentbullet.com/#!/home
Xavier closes the School after many of his students and faculty leave due to the Vietnam War (DoFP)
Hank is the only one still living at the School, he provides a serum for Charles which helps him walk again at the cost of his mutant powers (DoFP)
Mystique rescues fellow mutants, Havok, Toad, Ink, and Spike in Saigon (DoFP)
THE TIME LINE SPLITS HERE
X-A time line continues here. Skip further down to go to the X-B time line.
Mystique kills Bolivar Trask at the Paris Peace Accords in 1973 (DoFP)
Trask Industries continues developing the Sentinel Program over the next 50 years due to the mutant threat that they believe is coming
http://www.trask-industries.com/#/home
Mystique is captured by the US government and handed over to Trask Industries sometime in the 1970's
Wolverine and Victor Creed (aka Sabretooth) join William Stryker's Team X program in the early 1970's (Origins)
Wolverine and Victor, along with fellow mutants, Agent Zero, Wade Wilson, John Wraith, and Fred Dukes head to Africa to obtain a rare metal known as Adamantium in 1979 (Origins)
Logan quits the team in after refusing to kill innocent people (Origins)
Logan relocates to Canada and and in the 6 year interim meets Kayla Silverfox, who is killed by Creed in 1985 (Origins)
Stryker finds Logan and offers to help him find Creed. Logan undergoes the Adamantium bonding process at Alkali Lake, giving him his metal skeleton and claws (Origins)
Sabretooth finds Scott Summers (age 15 or so) and delivers him to Stryker (Origins)
Wolverine tracks down a mutant named Gambit to get information on where Stryker is (Origins)
Logan discovers that Silverfox is not dead and that Stryker has her sister, Emma, along with other mutants held prisoner for experimentation. (Origins)
Wolverine kills Wade (now Deadpool), but is then shot in the head by Stryker with an Adamantium bullet which causes him to lose most of his memories (Origins)
Emma, Scott, and the rest of the escaped Mutants meet Xavier and leave with him via a helicopter (Origins)
Mystique is rescued or escapes from Trask Industries sometime in the 1980's or 1990's.
Xavier and Erik meet Jean Grey (age 15 or so) in 1986-1988 (X3)
Marie (aka Rogue) discovers her mutant ability to drain the life force out of people in the not too distant future from 2000 (X1)
Rogue meets Logan in Canada (X1)
Logan and Rogue are rescued from Sabretooth by Cyclops and Storm (X1)
Wolverine wakes up the X-Mansion and meets Charles Xavier for the 2nd time (first time was when Charles and Erik try to recruit him in FC) and Jean Grey (X1)
Mystique kidnaps Senator Robert Kelly (X1)
Magneto uses his mutation machine on Sen. Kelly which ends up mutating him into an unstable blob like creature (X1)
Mystique infiltrates the Xavier School and convinces Rogue to leave before sabotaging Cerebro (X1)
Magneto and his Brotherhood, consisting of Mystique, Toad, and Sabretooth, kidnap Rogue from a train station (X1)
Sen. Kelly arrives at the X-Mansion after escaping from Magneto's lair, but dies (X1)
Xavier uses Cerebro to try and locate Rogue, but ends up in a coma due to the malfunctioning Cerebro (X1)
Jean uses Cerebro to find Rogue and Magneto's plan (X1)
The X-Men fly to Liberty Island to stop Magneto from using his machine to turn the world leaders into Mutants (X1)
During the battle, Toad is killed and presumably Sabretooth (X1)
The X-Men stop Magneto from unleashing his plan but not before some of the radiation from the wave affects Jean (X1)
Magneto is arrested and put into a plastic prison (X1)
Mystique ends up impersonating Sen. Kelly (X1)
Logan heads to Alkali Lake to find answers (X1)
Sabretooth tracks Logan to Canada and the two discover they have more in common than they thought (X2 prequel comic)
Stryker's team kills Sabretooth by using adamantium bullets as he kicks Logan out of a helicopter to save him (X2 prequel comic)
Kurt Wagner (aka Nightcrawler) attacks the President of the United States under the guise of mind control in 2004. He is shot before he can deliver the killing blow (X2)
William Stryker convinces the President to lead an attack on the X-Mansion/School (X2)
Jean and Storm find Kurt in Boston (X2)
Scott and Xavier visit Magneto in his plastic prison, but are ambushed by Stryker's men and Lady Deathstrike (X2)
Stryker leads an attack on the X-Mansion to try and get Cerebro, he ends up finding Wolverine there (X2)
Logan, Bobby (Iceman), Rogue, and John (Pyro) escape the mansion and head to Bobby's parents house (X2)
Mystique injects one of Magnetos security guards with Iron so he can use it to escape his prison (X2)
Logan, Bobby, Rogue, and John escape the police and military with the help of Jean and Storm in the Blackbird, they end up meeting with Magneto and Mystique in a forest (X2)
The X-Men go to Alkali Lake to find Xavier, Scott, and the rest of the mutants from the School (X2)
Stryker has built his own version of Cerebro which he plans on making Xavier use to kill all the Mutants in the world. He is able to do this by using his son, Jason, to mind control Xavier. (X2)
Wolverine kills Lady Deathstrike (X2)
Magneto's real goal is revealed when he tells Jason to tell Xavier to kill all the humans instead (X2)
The X-Men are able to save Xavier, Cyclops, and the other mutant kids before the base floods, killing Jason and Stryker (X2)
Magneto and Mystique escape, but not before Pryo joins them (X2)
The X-Men try to flee the flooding, but the Blackbird can't lift off so Jean sacrifices herself to shield the plane while it takes off. (X2)
A Phoenix can be seen flying just under the water of the lake a while later (X2)
Worthington Labs announces a cure for the Mutant gene in 2006 (X3)
Beast is now head of Mutant Affairs for the US Government (X3)
Mystique is captured by the US Government (X3)
Magneto and Pryo rescue Mystique, Juggernaut, and Multiple Man from a convoy, but during the rescue, Raven is stuck with the cure and de-powered (X3)
Scott goes to Alkali Lake to find Jean, but ends up getting killed when Jean's Phoenix persona unleashes itself (X3)
Logan and Storm track Scott to the lake and find Jean (X3)
Jean heads back to her childhood home where both the X-Men and Brotherhood show up, trying to co hearse her to their own side (X3)
Jean ends up killing Xavier and leaves with Magneto (X3)
Rogue decides to take the cure so she can be with Bobby (X3)
Warren Worthington the 3rd (aka Angel) arrives the X-Mansion seeking solace (X3)
The X-Men (Wolverine, Storm, Beast, Kitty Pryde, Iceman, and Colossus) head to Alcatraz Island to stop the Brotherhood from killing Leech, the boy providing the means to create the cure (X3)
Magneto moves the Golden Gate Bridge to fly his Brotherhood army across the waters (X3)
During the ensuing battle, many mutants are killed including Pyslocke, Kid Omega, Arclight, and Callisto (X3)
Logan is forced to kill Jean to stop the Phoenix from killing everyone else (X3)
Magneto is de-powered when Beast sticks him with the cure (X3)
Beast is announced as the new United Nations Ambassador by the President (X3)
Magneto is seen moving a chess piece cluing us in that the cure may not be permanent (X3)
Xavier's voice can be heard coming out of a comatose patient in Moria's care (X3)
Mutant Inhibitor Collar developed by Trask Industries in 2009 (http://www.25moments.com/#!/moments/2009)
Trask Industries Acquires Xaviers School for Gifted Youngsters (http://www.25moments.com/#!/moments/2010)
Angel (Warren Worthington the 3rd) is killed during a march on the X-Mansion by Sentinels in 2011 (http://www.25moments.com/#!/moments/2011)
Trask Industries announces the Sentinel Mark X in 2013 (http://www.25moments.com/#!/moments/2013)
Logan, now living in the Canadian wilderness, is approached by Yukio in 2013 (TW)
Yukio and Logan fly to Japan so Yashida can repay a debt to Logan (TW)
Logan meets Mariko and Lady Viper (TW)
Viper inserts a device which nullifies Logan's healing factor (TW)
Yashida dies (TW)
Mariko and Logan flee an attack during Yashida's funeral and retreat to Nagasaki (TW)
Mariko is kidnapped by the Yakuza and delivered to Viper's base in the village of Yashida's birth (TW)
Logan and Yukio head back to the house of Yashida where Logan removes the device which was nullifying his healing factor (TW)
Viper is killed by Yukio during a fight (TW)
The robotic Silver Samurai fights with Wolverine and ends up cutting his Adamantium claws off due to a special sword (TW)
It is revealed that Yashida is in the Silver Samurai and wants Logan's bone marrow to produce a youth formula to give him eternal life (TW)
Mariko kills her grandfather to stop his plan (TW)
Logan is approached by Xavier and Magneto at an airport in 2015 with hopes that he will help them fight a war that is coming (TW)
Hank McCoy is killed by an angry mob in New York in 2015 (http://www.25moments.com/#!/moments/2015)
8 years pass, during this time the Sentinel Program has advanced to a point where they are now actively hunting and capturing mutants. And in some cases, killing those that resist. Mutants are branded with an M over the right side of their face and put in holding camps while being forced to wear inhibitor collars. The Sentinel Mark X, using the abilities sourced from Mystique 40 years ago, are now the ultimate threat to the Mutant population. During these years, Angel, Beast and many others have been killed. Rogue has been captured and imprisoned.
The X-Men, now consisting of Wolverine, Kitty Pryde, Iceman, Colossus, Storm, Warpath, Sunspot, Blink, Bishop, Xavier, and Magneto have one last chance to fix the present by sending Logan back to his younger self in 1973 (DoFP)
X-B time line continues here
Logan awakes in his 1973 self with the knowledge of what the future brings (DoFP)
Logan finds Xavier and Beast and convinces them of what needs to be done (DoFP)
The three of them find Peter Maximoff (aka Quicksilver) to help break Erik out of prison (DoFP)
Logan, Charles, Hank, and Eric head to Paris to stop Mystique from killing Trask, but in doing so out themselves to the public (DoFP)
Trask uses this scenario to convince Nixon to go ahead with the government funding for the Sentinel program (DoFP)
Erik sabotages the 8 Sentinels by infusing them with metal while they are on a train to Washington DC (DoFP)
During the unveiling of the Sentinels, Magneto lifts an entire stadium and flies it over to the White House to seal in the President and keep ground forces from interfering with his plan (DoFP)
Using the Sentinels to attack the humans on live TV, Erik tries to turn the tables in favor of himself and use them to kill Nixon (DoFP)
Mystique, disguised as Nixon, shoots Erik to stop him and in turn decides to not kill Trask (DoFP)
The Sentinel program is cancelled and Trask is arrested for selling military secrets (DoFP)
Mystique, posing as Stryker gets Logan out of the lake (DoFP)
Gambit is introduced (198?)
The X-Men must stop Apocalypse (198?)
Logan wakes up and is shocked to see Jean and Scott alive and well at the school back in 2023 (DoFP)
Xavier probes into Logan's mind for a brief moment and sees the old time line (DoFP)
Q and A time!
Q: Xavier was killed in X-Men 3, how did he come back?
A: If you stayed to the end credits of X3, you would've seen this...
http://youtu.be/ZSkn3KYwmtc
Xavier transferred his consciousness into the body of the comatose man right before he was vaporized by Jean.
Followed by this scene during the credits of The Wolverine
http://youtu.be/EfC5i0AmAJg
Q: What? That's dumb, why does he look like him and why can't he still walk?
A: In the commentary track for X3, Brett Ratner confirmed that they played loose with the idea of Charles' twin sister Cassandra Nova http://en.wikipedia.org/wiki/Cassandra_Nova from the comics. Instead of a sister, they made it a twin brother. This is backed up by an interview with Bryan Singer. As for why he still can't walk, you could say that his legs had atrophied from not moving for so long.
Q: Why does Logan have metal claws in DoFP when they were bone at the end of The Wolverine?
A: There is no real answer for this, but you can assume Magneto played some part in that.
Q: Is Quicksilver the son of Magneto?
A: Yes. This is even joked about in the movie when Peter mentions his mom used to date a guy that could control metal. There is also a shot of the mom watching TV in horror when Erik is shown causing terror at the White House, signifying that she knew him.
Q: How come Moira looks to be about 40 in X3, but was 30 in First Class, which took place 45 years earlier?
A: The real answer is the movie makers not giving a shit, but we can say it's her daughter who happens to have the same name.
Q: Wasn't Emma Frost in Wolverine: Origins before she was in First Class?
A: Yes and no. She is never called Emma Frost in the Wolverine movie and her credit is technically only Kayla's Sister. Again, the movie makers probably thought it'd be a nice easter egg for the fans, so write it off as only that.
Q: Xavier said he met Erik when he was 17 and they built Cerebro together in X-Men 1, what's up with that?
A: That's just a case of the writers going oops. Singer has said he regrets putting that line in X-Men 1. As for building Cerebro, they kind of did, in a way. Sure Hank actually built it before meeting them, but Charles and Erik were the ones who got it working.
Q: How come we see Xavier walking in X3 and Origins in the 80's when he was paralyzed in 1962?
A: Again, oops. The guys who made First Class should've held off on that one, but you can use the excuse that Charles took the serum Hank made which gave him the ability to walk. Sure his powers are supposed to be dormant, but maybe during the 15 or so years, Hank developed a better version of it which didn't have that side effect? Who knows, it's just one of those things you'll have to live with.
Q: How come Stryker in Origins is like 20 years older than he is in Days of Future Past?
A: Well since Origins sucks so much, just ignore 98% of that movie and don't harp on it
Q: Wait a second, wasn't there ALSO a Stryker in First Class who was like 60?
A: Yep, that was William's dad. Charles even says, No Agent Stryker, although I could ask you about your son, William...
Q: How come Sabretooth doesn't seem to know who Logan is in X-Men 1 even though they're brothers and fought together for over a hundred years?
A: Cause Origins sucks. They shouldn't have been brothers in the first place, but Victor seems to be dumber and more animal like than he was before. He did collect the dog tag after all and keep it as a souvenir.
Update to this answer - There is actually a canon comic book prequel for X-Men 2 that tells the following story
Sorry, visit the site to read the synopsis, this post became too long and I couldn't add any more text...
http://marvel.wikia.com/X-Men_2:_The_Movie_Prequel_Vol_1_1
Q: Aren't Havok and Cyclops brothers in the comics? How can Havok be in his late teens/early 20's in First Class while Scott is only like 30 in X-Men 1?
A: Chalk one up for the movie makers not giving a shit and wanting to use whoever they thought would fit in their movie at the time. I believe if they make any connection between the two, that they'll say Alex is Scott's dad.
Q: If Mystique is the one who ends up fishing Logan out of the water at the end of Days of Future Past, will that mean he won't get his Adamantium?
A: We won't know until the next movie comes out, but there are ways for it to happen. Mystique could be working with Stryker or will end up making a trade. The other theory is that Apocalypse will turn Logan into one of his Horsemen and in doing so will give him the Adamantium skeleton and claws like in the comics.
Q: Didn't I see a young Storm in First Class during one of the Cerebro sequences?
A: You may have seen this...
Which again, could just be an Easter Egg and not really Ororo as she looks about 13 or 15 in that photo which would make her almost 60 by the time X-Men 1 rolled around and that's obviously not correct.
Q: Why did Anna Paquin get a higher billing than Ellen Page in Days of Future Past when she was in like one scene?
A: There was an entire cut sequence of Charles, Erik, and Bobby rescuing her from a Mutant Camp. Singer has said it will be on the Blu Ray with full effects.
Q: Did Days of Future Past make X1-3, Origins, and The Wolverine all completely useless?
A: Kind of. We don't really know what actually sticks from those movies until we see the next movie(s). The writers have hinted that some of the events may still happen, but just in alternate ways.
Q: Where were all the Sentinels during X1-X3?
A: They were around, but not actively hunting mutants. They acted as peace keepers and security during major events in history from 1973 onwards. We even see one of the Sentinel heads during the Danger Room sequence in X3. This may have been a Mark 7 or 8 design. The Mark X models didn't come into being until 2020 or so.
Q: If Mystique was captured by Trask Industries in the X-A time line, how was she in X-Men 1?
A: We don't know for sure, but it's assumed Magneto and his Brotherhood broke in to rescue her. That, or she escaped somehow.
Q: How does Kitty have the power to send someone's mind back in time? She can't do that in the comics.
A: This was a nod to the comics where Rachael Summers sent Kitty's mind back in time instead of Logan's. Since Rachael isn't in the movie-verse and Kitty wouldn't have been alive in 1973, Wolverine was chosen to go instead. You could stay it was her secondary mutation, as some characters get as they get older.
Q: Why did they rescue Magneto in the first place in DoFP?
A: Well for one, Logan and Charles didn't know at the time that he would try to kill Mystique on first sight or pull some crazy scheme. Hindsight is 20/20. Charles figures it might've been easier if both he AND Erik were present to help persuade her.
Q: Why didn't they just take Quicksilver with them to Paris to stop Mystique?
A: Because... reasons? The movie would've been over in 4 seconds and that's no fun. Plus, he's a cocky teenager, maybe he wouldn't follow orders or do something worse? He was way too overpowered in the movie anyways. Quicksilver is only supposed to be able to run at about 700 mph, yet in the movie he was on Flash levels of power.
Q: How did Pietro hear his music while he was running so fast?
A: He played his tapes on super fast forward, who cares, it was a fun scene!
Lionel Mandrake asks
Q: Why does Bolliver Trask look so different in X-Men: The Last Stand?
A: Trask in X3 was only called Secretary Trask, so we can make the assumption that it's not the same guy. They just happen to share the same last name. Though in reality, yes, it was supposed to a nod to Bolivar.
Q: If Trask used Mystiques abilities for the Mark X Sentinels, how come they can mimic powers? Her mutant ability doesn't allow her to take on the powers of the people she copies. Wouldn't it make more sense if they had Rogue's powers?
Kai Dracon states
The Mark X Sentinels didn't seem to literally copy mutant powers like Rogue does. Rather they're made of nanomachines (son) which were created with insight from Mystique's physiology - the way her cells can reorganize themselves like, well, nanonmachines. (Son.)
So the Mark X's would analyze the combat scenario and reconfigure their armor to counteract the effect of a mutant power. But we didn't see them copying stuff like Storm's weather control or Xavier's telepathy. In fact if they could copy stuff like that they'd be even more deadly, truly unstoppable. (Army of telepathic Sentinels just orders every mutant to kill themselves.) They also knew how to counteract Bishop's power by overloading him but none of them copied his actual ability which is why energy attacks worked on them.
Q: Who was that little girl with Quicksilver at the end of the movie? Was that supposed to be Scarlett Witch?
A: It might have been at the beginning, but Bryan Singer is quoted in Empire Magazine that the girl is NOT Scarlett Witch, aka Wanda Maximoff. In the interview he says that there was a cut throw away line where the little sister is bugging Peter and the mom interjects by saying, "Go upstairs and bug your sister!". The sister upstairs was intended to be Wanda.