Time Machine

The Time Machine was built by Future Bulma in Future Trunks' devastated timeline, where Androids 17 and 18 had destroyed civilization and killed most of the Z Fighters. With no other option available to save their world, Bulma dedicated years of research to developing a vehicle capable of traveling backward through time. The machine's small, egg-shaped cockpit can hold only a few passengers, and it requires a significant amount of fuel for each trip.

The creation of the Time Machine is considered a grave violation of the natural order. Beerus described altering the flow of time as a sin, and Whis noted that each trip to the past generates a new alternate timeline rather than changing the original one. This fundamental property means the Time Machine cannot truly "fix" the timeline it came from; it can only create branching paths where different outcomes play out.

The Time Patrol, led by the Supreme Kai of Time, considers the construction and use of time machines to be a serious crime. In the Xenoverse series, Chronoa confronted Future Trunks about his use of the machine and recruited him into the Time Patrol as a form of atonement.

The Time Machine's usage created multiple divergent timelines, adding layers of complexity to the Dragon Ball narrative. Future Trunks' first trip to the past created a new timeline where the Z Fighters received advance warning about the Androids and the heart virus medicine for Goku. However, this new timeline developed its own differences: the Androids appeared earlier than expected, Dr. Gero was still alive, and Cell emerged from yet another timeline.

Cell's timeline represents the most convoluted consequence of the Time Machine's existence. In that timeline, a different Future Trunks successfully defeated the Androids using the Shut Down Remote, only to be killed by Cell, who then stole the Time Machine and traveled further into the past to find the Androids in their complete forms.

The Time Machine returned prominently in Dragon Ball Super during the "Future" Trunks Saga. After Goku Black and Future Zamasu devastated Future Trunks' world, the machine became his only lifeline for seeking help. Bulma in the present timeline later attempted to repair it using fuel notes left by her future counterpart. The saga culminated with the Time Machine ferrying Goku back to the future to summon Future Zeno, who erased the entire corrupted timeline.