25th century

Multiple realities

(covers information from several alternate timelines)

The 25th century was defined in the calendar of Earth as being from 2401 until 2500. The century started off with the 250th Frontier Day celebration which was hijacked by a Changeling/Borg plot to destroy Starfleet and the United Federation of Planets. The plot was thwarted by the former command crew of the USS Enterprise-D and resulted in the destruction of the Borg Collective and its queen.

Decades

A message sent in 2364 by the USS Enterprise-D from the galaxy known as M-33 is within receiving range of Starfleet in this year. (TNG: "Where No One Has Gone Before")
In 2365, Doctor Katherine Pulaski predicted that the Mariposans would have died out by this year, as a result of replicative fading, leaving behind their developed world with cities ready for colonization by the Federation. (TNG: "Up The Long Ladder")
In 2378, the crew of the USS Voyager expected they would reach Federation space in this year on stardate 92690.8. (VOY: "Endgame" display graphic; [1])

If Quark had sold a small cloaking device and Odo found out about it in 2370, this is when the fifty year sentence the Changeling threatened, in which he would dig trenches at a penal colony, would end. (DS9: "Profit and Loss")

Solosos III is expected to become inhabitable for Humans again. (DS9: "For the Uniform")

According to Benjamin Sisko in 2371, Meridian returns to the prime universe in this year. (DS9: "Meridian")

In 2371, at the very beginning of their journey home, this was the year the crew of Voyager expected they would reach Federation space. (VOY: "Caretaker")

In 2372, Jadzia Dax predicted that Miles O'Brien would die peacefully in bed this year surrounded by family and friends. (DS9: "To the Death")

According to Q in 2372, around this year, Humans will be in the Delta Quadrant. (VOY: "Death Wish")
Sometime during this century, the methods or materials that had been used to construct starships since the 23rd century, such as the USS Discovery, were no longer used. (DIS: "People of Earth")
Sometime during this century, Barzan II joins the United Federation of Planets. (DIS: "Die Trying")

The following events take place in an alternate timeline in which Alexander Rozhenko chooses to never become a Klingon warrior. (TNG: "Firstborn")

Alexander announces that the House of Mogh is ending its feud, adding that there would be no more retribution or revenge. Though warned by his father, Worf, the enemies of the Great House see Alexander's weakness and move against him, resulting in the death of Worf on the floor of the Great Council Chamber.

The following events take place in an alternate timeline in which Benjamin Sisko is displaced out of time. (DS9: "The Visitor")

Nog is a Starfleet captain. Jake Sisko asks Jadzia Dax and Julian Bashir to help Jake free his father from his displaced time. Nog gets the USS Defiant out of retirement and Worf obtains permission to enter Bajoran space.

Jake Sisko dies, thus releasing his father from the subspace link that ties them and negating this timeline.

Going by Data's statement that the energy ribbon from Star Trek Generations passes through the Milky Way Galaxy every 39.1 years, it can be expected to return in 2410, 2449, and 2488.
According to the Star Trek: Picard Logs, the USS Titan-A was launched in 2402. [2] Terry Matalas has since confirmed that this was an error and that the Logs were meant to list the launch date as 2401. [3]

In the game Star Trek Online, Humans reach the Delta Quadrant in the year 2410, along with the Romulan Republic and the Klingon Empire, through the use of Dyson spheres and Iconian gateways. This contradicts the Q's prediction of Humans reaching the Delta Quadrant in 2472. This year also sees the Iconians return from exile in the Andromeda Galaxy and engage in a massive invasion of the Milky Way, forcing all the major powers of the galaxy to join together to fight them.