Hmm...

Slowing down time is possible. It just takes inordinate amounts of energy to do so. 'bout... 3-4 Suns.

As is moving objects through time. Although it doesn't cost as much, apparently.

(Yeah, I don't know what I'm talking about. I am studying for my physics final, but... >.> ::too easily distracted:: hell, this wasn't even related to harmonic motion.)