Dan's "shifts" through time occur seemingly at random. The only indication he has to an oncoming jump is a feeling in his head which varies from right before he jumps to several seconds of warning. Initially, the feelings were headaches. However, as the series progresses the headaches become less painful. Dan appears to have no control over the shifts. The first jump is several decades into the past; through a series of jumps, he jumps nearer to the present, usually years at a time. When Dan met Evan in the series finale, Evan told Dan that he was a traveler too. It was implied that Evan had traveled to different time periods at random. The same can be inferred with Livia, who claims that she has gone through many jumps of her own. But her jumps are quite different from Dan's.