Memory Alpha
Memory Alpha
Mirror Universe
(coexisting on another dimensional plane)

The Terran Empire flag on Luna

The flag of the Terran Empire, which displays the imperial symbol rendered in gold on a field of crimson, is planted on Luna. (ENT: "In a Mirror, Darkly", "In a Mirror, Darkly, Part II")
The astronaut on the moon is seen wearing a EV suit still in use in the mid-22nd-century, suggesting a date much later than the prime universe moon landing in 1969.
Zefram Cochrane launches Earth's first warp vessel. The Vulcans make First Contact with the Terran people. During first contact, Cochrane kills the Vulcan captain and his fellow Terrans storm the Vulcan ship. (ENT: "In a Mirror, Darkly")

Attack on the Lunar colonies

Late 21st century to mid-22nd century 
Sometime between 2063 and 2155, The Lunar colonies are attacked by an Emmette-type starship, with photonic torpedoes. (ENT: "In a Mirror, Darkly", "In a Mirror, Darkly, Part II") The Terran Empire conquers the Vulcans, Andorians, Tellarites, Denobulans, and the Orions. Starfleet engages in a conflict with the Xindi. (ENT: "In a Mirror, Darkly", "In a Mirror, Darkly, Part II")
As the Imperials struggle to put down a massive rebellion, the ISS Enterprise discovers the USS Defiant, which has been lured from the primary universe 100 years in the future (TOS: "The Tholian Web"). After a brief power struggle on board the Defiant, Hoshi Sato takes command and declares herself Empress. (ENT: "In a Mirror, Darkly", "In a Mirror, Darkly, Part II").
The USS Discovery, under Captain Gabriel Lorca, is brought to the mirror universe with the use of its spore drive. (DIS: "Despite Yourself")
A transporter accident brings several personnel from the primary universe to the mirror universe. James T. Kirk-prime encourages mirror-Spock to start a revolution. (TOS: "Mirror, Mirror")
Late 23rd century to early 24th century 
Sometime between 2267 and 2270, Spock becomes commander-in-chief of the Terran Empire and implements several major reforms, turning the Empire into a more peaceful and less aggressive power. Prior to the full enactment of these reforms, the Terran Empire forces occupy Bajor. Spock's reforms leave the Empire unprepared to fight against the Klingon-Cardassian Alliance. The Alliance conquers the entire Terran Empire, enslaving the Terrans and Vulcans. (DS9: "Crossover")
Benjamin and Jennifer Sisko separate. (DS9: "Through the Looking Glass")
Julian Bashir and Kira Nerys become the first people from the primary universe to cross over to the mirror universe in one hundred and three years. Quark is executed. The primary Doctor Bashir kills Odo. (DS9: "Crossover")
The Terran Rebellion begins. Benjamin Sisko is killed when his freighter is destroyed. Garak executes Rom. Miles O'Brien becomes leader of the Rebellion. (DS9: "Through the Looking Glass")
The Rebellion takes Terok Nor. The rebels build a Defiant-class starship, the ISS Defiant, based on schematics stolen from the primary universe. It helps the rebels to remain in control of Terok Nor. Intendant Kira Nerys kills Nog and Jennifer Sisko. (DS9: "Shattered Mirror")
The mirror universe versions of Bareil Antos and Kira Nerys cross over to the primary universe to steal an orb. The Intendant hopes the Orb of Prophecy and Change will unite the mirror Bajorans against the Alliance. (DS9: "Resurrection")
Jadzia Dax is killed in a skirmish with the Alliance. Kira kills Brunt. Garak is killed by an ulcartic virus. Ezri Tigan joins the Rebellion. After a battle between the ISS Defiant and the Regent's flagship, The Rebellion captures Regent Worf. (DS9: "The Emperor's New Cloak")