Past events and ending of "X-Men: Days of Future Past" takes place.
Due to Wolverine's interference with the old universe, a new one has been created in it's stead. In this universe, a future exists where Rogue is no longer missing but is seen happily with Iceman. Shadowcat and Colossus are seen teaching a class, with Beast roaming the halls. Storm is also seen praising students, while Jean Grey and Scott Summers are in Xavier's office. Charles Xavier, along with all the previously mentioned characters, have all been resurrected. Logan is now a History teacher, and Charles promises to catch Logan up.
What is a likely major change is that Jean Grey was never forced to remain behind at Alkali Lake. She does not seem to be influenced by the Phoenix persona, and Cyclops is still alive.
James Howlett left his bodyguard job in 1973 to find Charles Xavier, and in the process found Hank McCoy and introducing himself as Logan.
Logan's knowledge of the future led to them finding Quicksilver (Pietro Maximoff), who they used to break Magneto out of the Pentagon (his means of escape in the Prime timeline is unknown).
Xavier and Magneto's actions led to Mystique's assassination being thwarted, but led to her, Beast, and Magneto being seen and recorded publicly.
The Sentinels were then expedited in production, but laced with metals by Magneto. This allowed him to set center stage inside the White House, where he would kill President Nixon and Bolivar Trask. Mystique prevented this and spared the humans as an act of mercy. Magneto and Mystique parted ways with Xavier and Beast. Mystique saves Logan from drowning under the guise of Major Stryker.