Time dilation is a phenomenon where one person’s clock is moving at a slower rate than another person’s clock - showing that time has slowed for that individual.
Albert Einstein’s Lorenz Transformation shows that time dilation can be forced through motion. In other words, time can be changed through motion ("Moving clocks run slow").
A passenger in a spacecraft moving at a great speed would experience time moving at a slower speed than would be experienced back on earth. So, for example, if a ship is moving fast enough, time relative to the craft might be one year, where ten years of time have passed on earth below. This phenomenon was explored in Planet of the Apes by Pierre Boulle.
Time dilation only allows for traveling forward in time.