The closest I've had to it was a lucid dream where I was interacting with somebody I really fancy and the dream created a false memory of spending hours together. I suppose we should be able to simulate time dilation intentionally similar to the way we can use the Jedi mind trick on dream characters.
I can make things float to the ground that usually should fall very fast if that counts as "Slowing time down"
Thought proces can be much faster, so like instantly understand a whole concept. A DC who can give an instant feeling or an understanding of things, not as slow as when in converstation. It feels like conversating at topspeed. This could be mistaken for telepatie or special guides from another realm. But it still feels very special and I think people may trust their own capacity more, why wouldn't it be your own mind capable of cool ways of thinking?
Last month I had a weird dream where time stood still. We were flying in a light aircraft at the time and we just stopped mid-air!
I've also experienced a lucid where I saw the whole of someone else's life flash before me, like I was doing a memory dump. Very surreal!
Time in lucid dreams has always pretty much seemed 1:1 for me. I only experience dreams that feel like they take up longer spans of time when I'm not lucid, as time dilation in dreams, for me, seems mainly to rely upon transitions that go by unnoticed, but, when lucid, a change of scene is very apparent.
Listen and relax while you post...