May be unable to move to a different location spatially, and instead just end up in the same location in a different timeline. Telefrag is possible as a result.
Protection conjecture, a cause that prevents the change of the past, could interfere with the Time Travel in some cases. If not and the past is change, results in the present time, before the travel, can have unwanted results.
Time travel may separate the user from space, which would leave them entrapped within time, rendering them biologically immortal, intentional or not.
Abuse and misuse of time travel may result in one's mind losing track in time, causing the body to age but the mind to remain young.
Because of the complexities and potential dangers, time travel is sometimes considered a taboo and against the law of nature, and even outlawed by some governments.
Cannot interfere in certain matters concerning the flow of time and space.
It's not known if the future is protected by the same cause the past is (see Precognition for more info how changes to the future could be prevented).
May distort the space-time continuum in exchange for traveling.
May only be able to transport living tissue through time.
May only be able to go either backward and forward in time.
May only be able to travel the duration of their own lifetime.
Time travel to the past may create an alternate timeline, in order to prevent changes to affect the original time. This means that the past would branch off into a new dimension of time, while the present timeline would continue as though nothing affected the past. This prevents intended changes.
Trunks' (Dragon Ball) time machine allows him to travel to the past.
Time Rings (Dragon Ball Super)
Ultear Milkovich (Fairy Tail) after becoming one with Time itself became a time traveler of the temporal world.
Kagerō (Flame of Recca) using Jikuryūri, which allows her to travel through time via a portal, but it traps her within time itself, rendering her immortal.
Kurei Mori (Flame of Recca) using Jikuryūri to open a time portal in space, but cannot become immortal so he does not have to worry about being trapped in time.
The Bone Eater Well allows Kagome and InuYasha (InuYasha) to travel between the 500 years of Sengoku and current eras.
Seiryu (Magic User Kurohime) is the wind spirit, and can manipulate space-time the wind just floats through it freely, even allowing others to travel back through time.
However, when Pryce (Pokémon Adventures) forced Celebi to travel back in time, it adversely caused temperature dropping to absolute zero and the world completely freezing.
Sailor Pluto (Sailor Moon) is the guardian of the Door of Time.
Backlander (Dinosaur King)
Karasuki (Boruto: Naruto Next Generations) is an artefact that takes the shape of a turtle-like device when activated, used only by the Ōtsutsuki Clan members only, that allows them to travel through time.
Kurumi Tokisaki (Date A Live) can send others or herself into the past using her twelfth bullet Yud Bet, traveling through time.