A is for Aeon, the timeship piloted by 29th century Captain Braxton during his most notable encounter with Captain Janeway and the USS Voyager.
B is for Berlinghoff Rasmussen, a time traveler who came aboard the Enterprise-D, after stealing a time-pod.
C is for Correct change, which Kirk and Spock lacked in order to ride the San Francisco transit bus back in 1986.
D is for Data's head, which is 500 years older than the rest of his body thanks to time travel.
E is for Enterprise, which travelled through time occasionally.
F is for Firstborn, the episode in which Alexander Rozhenko travels back in time to change his future.