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.
G is for George and Gracie. Two humpback whales from 1986 who were transported three hundred years into the future to save Earth.
H is for HMS Bounty, the ship which traveled back in time to get those humpback whales.
I is for implosion. Caused by the detonation of red matter. Which leads to the creation of a time-traveling wormhole.
J is for Janeway. Captain Kathryn Janeway. The bane of a future Federation timeship captain's existence.
K is for Kirk, James T. Who was according to at least one Temporal Agent was a menace with seventeen seperate temporal violations.
L is for Lily Sloane, who Captain Picard met while time traveling.
M is for Madeleine, who couldn't help but interrupt Dr. Nichols at Plexicorp at a sensitive moment.
N is for Nexus, the realm where one's thoughts shape reality and time was not linear, and allowed Kirk to travel to the future with Picard.
O is for Orb of Time, used by Arne Darvin in an attempt to kill JTK.
P is for Prison Guard. That Kirk overwhelms to escape from a jail cell on Sarpeidon hundreds of years in that planet's past.
Q is for Quark, who ended up making an unofficial First Contact between Ferenginar and Earth due to time travel.
R is for Romulan. For a time the writers of ENT were thinking that "Future Guy" might be a Romulan.
S is for San Francisco...a seemingly very popular destination for time traveling Starfleet officers.
T is for Temporal Prime Directive.
U is for USS Bozeman, which was caught in a time-loop with the Enterprise resulting in it's repeated destruction.
V is for Visionary, a DS9 episode involving time jumps
W is for World War II, an alternate-timeline version of which Jonathan Archer and the NX-01 crew visited in the closing days of the Temporal Cold War.
X is for Xindi, easily manipulated by a faction from the Temporal Cold War
Y is for Yesterday's Enterprise, in which the Enterprise-C changed the current timeline by moving forward in time.
Z is for Zephram Cochran, who the Enterprise E also encountered in the past.