Apart from obviously being nonsense, does the following sort-of make sense (and, for bonus points, has anyone ever used this idea in fiction before):
“Let us suppose you travel at a little below the speed of light, and that for every second of ship time, a hundred seconds would pass externally.”
“Okay,” said Louie, concentrating hard and trying to ignore the constant discomfort of the ship’s acceleration.
“So, you complete a return journey that takes you a month, but you find that a hundred months have passed for everyone who stayed behind,” continued the machine. “In effect, the problem that cronium has to solve is not how long the journey takes for you, but how long it takes for a everyone else.”
“And that’s where the time-travel comes in?”
“Exactly – in the example I gave you, a cronium-shift during flight would gradually move you ninety-nine months into the past. The result would be that the journey would now have taken a month from all perspectives – stationary and moving.”
“I think I get it now,” said Louie. “But isn’t it dangerous? I mean, couldn’t you end up changing history or something?”
“Not at all,” said Cassita. “The shift available never allows you to arrive prior to your departure. Causality is always preserved”
“So I don’t get to kill my own grandfather?”
“Why would you want to do that?” said Cassita. “Was he unpleasant?”
Louie laughed. “No, he was really nice – well, one of them was. It’s just what people always say when time travel comes up.”
“Ah, I see. A paradox.”
... and if it does make sense, anyone want to tell CERN?