Memory Alpha
Memory Alpha
Multiple realities
(covers information from several alternate timelines)

Archer and Daniels observe the time stream resetting itself

A time stream was a term relating to the flow of time.

Aboard the NX-class starship Enterprise, Daniels used the phrase "time stream" to refer to the fluctuations in the timeline that resulted in the alternate timelines that were created when the Temporal Cold War turned into an all-out conflict. (ENT: "Storm Front")

During his attempt to commandeer the USS Discovery on stardate 2136.8 using temporal loops, Harry Mudd noted that ending the loops and allowing the Discovery to rejoin the time stream would be an irreversible action. After he did, the time crystal he used to generate the loops disintegrated. (DIS: "Magic to Make the Sanest Man Go Mad")

A time stream, as it appeared on the navigational display of a runabout

In 2372, Harry Kim intersected with a time stream while piloting the shuttlecraft Drake in the Delta Quadrant. This had the effect of changing history in that Harry was never assigned to the USS Voyager and instead had a position at Starfleet Headquarters in San Francisco. While in this alternate timeline, Harry met an alien from a temporal inversion fold in the spacetime matrix, who had taken the form of a Human named Cosimo. Cosimo detailed to Harry the events which led to the creation of the alternate timeline, and informed him that the time stream, which wove throughout the galaxy like a thread, could be intersected again, possibly repairing the damage to the timeline. If not, he could be sent before the formation of life on Earth or a billion years into the future. With the help of the alternative Tom Paris, Harry was able to locate and fly into the time stream, recreating the exact conditions which resulted in the change to history in the first place, and undoing the alterations to the timeline. (VOY: "Non Sequitur")

Timeline reset

Several images of historical importance were seen when the timeline reset. (ENT: "Storm Front, Part II")

Images seen during timeline reset