The Flash, Season 1

Wells:
You ruptured the time continuum, didn't you? You're experiencing temporal reversion.

Barry:
Yeah!

Wells:
How long?

Barry:
Uh, a day and some change. It's like I'm living it all over again.

Wells:
Yeah, well, that's good. That means there's not too much you could've messed up yet. How did this happen?

Barry:
I-I don't know. I mean, I was running faster than I've ever ran, and the first time that I lived this day some really horrible things happened. There was a tidal wave and...

Wells:
No. Do not tell me. I don't want to know anything about the future you experienced. Nothing!

Barry:
Okay, but Dr. Wells, I...

Wells:
Barry. Time is an extremely fragile construct. Any deviation, no matter how small, could result in a cataclysm. Now here's what you're going to do. Everything you did before. Every word you uttered, every step you took, you're going to do again. And you're not going to tell anyone this happened.