Granted. It only works for time, not space. You try to go back 30 seconds and find yourself 120 miles away from the surface of the earth. You got to use your power once, at least.

Granted. You can travel back in time but doing so alerts the Time Police from the 27th century who instantly track you down, take your ability away and imprison you for life.

Granted. You can only travel back in time 100 years at a time, and you can never return. You also take nothing with you, including your knowledge of the current time.