Thread:LoveWaffle/@comment-1713281-20140523071250/@comment-1713281-20140523190849

Kitty explained it before she sent Logan back. As long as Logan's mind is still in 1973, both timelines will coexist. As soon as Logan loses his grip and slips back into 2023, whatever changes he caused will take effect and become history, and that history will become the only history the rest of them know, hence Logan's mentions of being the only one to remember.