So here's number one.
Deja vu is triggered by a real memory: a memory of a dream that you had previously forgotten. But the dream is the tricky part, because that (whenever you originally had it) was a subconscious glimpse into the future. Perhaps the fabric of space-time DOES fold in on itself occasionally, but we can't perceive it unless we completely lack distractions, i.e. we are sleeping. Then it just happens that we see our future, forget it, then half-remember it when it actually happens to us.
Brilliant? Not at all. And I'm sure that I'm wrong about most of that nonsense. But I thought of it, so you had to suffer through it. (<- brilliant logic)
You may consider your day hereby ENLIGHTENED