It was assumed to be an alteration of the Matrix, it is a phenomenon that most people encounter several times in their lives; I, myself, have lived it pretty often. I'm talking about deja-vu.
Every once in a while it might feel like the same thing has already happened just the way it does at the time; and I want to know what is all of this about!
The thing is that there are no real theories behind the event; it can't be lab-s(t)imulated so it is nearly impossible to study it. So all the real ideas are as plausible as the fictional ones.
What's uttered is that deja-vu could be related to syndromes such as schizophrenia or anxiety or that it's a malfunction in the perception of memories, which would place stuff that happened milliseconds ago in a far distant period of time.
Opening the gate to other worlds, first we have dreams. The phenomenon is depicting something you've dreamed in a vivid moment; but dreaming something that particularly precise, ain't it wicked? (But I have a strong feeling that you'll be reading some other stuff about dreaming here soon.)
There's also the Matrix proposition, but that's a bit far-fetched.
And so we're left with the final explanation, which I tend to embrace in a supernatural way of seeing things even though Fringe is not my cup of tea...drum-roll...Deja-vus are glimpses of memories from other dimensions that the person has already visited. So our minds go wandering from time-place to time-place and their keep little tokens that come up when you except the least.
I guess that makes us all visionaries (if we could trigger the reenactment at any given instant) or is my dark side darker that I thought, with its deja-vus any other month...