system
Given the following post, respond as if you're commenting on Reddit:
human
[X-Men: Days of Future Past] At the very end of the film, why did Logan in the newly forged timeline suddenly wake up with his consciousness from the defunct super sentinel timeline?

As I understand it, from 1973 until the day he woke up in the future, Logan lived his life in the new timeline without any direct memory of being possessed by his defunct future self. (Xavier and Hank may have told him about this period, but that would have no effect on what ultimately happens at the end when he wakes up in the X-mansion.) So from Logan's perspective of the altered timeline, he just blacked out a few times during the movie's events and then woke up getting dredged from the river with his 1973 consciousness... so shouldn't that have been the end of his time related disorientation?

The only other alternative, in theory, would be that the sudden erasure of the super sentinel timeline caused a blast of spacetime-related energy. Such a blast amplified the time-defying telepathic connection, and so Logan's future mind was permanently transferred to his 1973 body. But obviously this was not the case because then he would've never been confused at all and Xavier would have nothing to explain to him at the end.

I do not understand what caused him to wake up one day with his future consciousness. I understand perhaps that date coincided with the date that the sentinels were erased, so it became a set point in the timeline that on that day, his consciousness would spill over. Which would mean it overlaps with the theory I posited about a spacetime related energy blast causing a telepathic time ripple, but with a slightly different effect that doesn't sit quite as well with me.

Did I just work myself through it? Maybe. But I would like to hear your theories or perhaps the mechanics were all officially addressed somewhere along the line.

Thanks for reading!
gpt
So the Logan that lived in the dark future of 2023 goes back to 1973 and prevents Mystique from killing the scientist.  This erases the original dark time line Logan is from so when his mind returns it returns to his body now living in the new 2023 where everyone is alive.

So either dark time line Logan completely replaces the mind of new time line Logan (which is kind of dark if you think about it, essentially killing the Logan that lived through the better time line) or as Logan settles into his body he will start to remember the new time line, but still retain the memories of the dark time line.