Board Thread:Questions and Answers/@comment-24510517-20140530190223/@comment-238662-20140530213430

Basically X-Men: First Class is the same. But then there was a 1973 where Mystique killed Trask which led to X-Men Origins: Wolverine, X-Men, X2, X-Men: The Last Stand, The Wolverine, the Sentinel filled future of Days of Future Past.

Then there is the 1973 where they stopped Mystique killing Trask which leads to the 2023 where there are no Sentinels and Jean and Scott and Beast are still alive. This is because the events of X-Men Origins: Wolverine, X-Men, X2, X-Men: The Last Stand and The Wolverine no longer happened or if they did happen they didn't happen the way we saw them, for instance we saw Scott and Jean die but in the New Timeline they didn't die because one of the events that led to them dying happened differently in the new timeline.