Whereever possible, I shall quote the source of the information of the entry in this timeline. Some entries may be conjectural since their dates were determined by the authors of the official "Star Trek Chronology". As mentioned before, I regard 25A as having occurred in 2268, and JR as having occurred in 2269. Therefore, events described in the computer entries as having happened at certain period in the past shall be dated according to the year of the game in which the entry first appeared in. For example, Dr. Breddell's dismissal from the Vardaine Science Council, described for the first time in 25A (2268) as having occurred ten years ago, took place in 2258 (2268 - 10 = 2258). It is also assumed that all years used in the Star Trek universe refer to Earth years unless stated otherwise.
More than 5 billion years ago The Guardian of Forever, a sentient time portal, is asked its last question prior to 2267. ("The City on the Edge of Forever" [TOS])
4.6 billion years ago The star that would one day be known as Sol began to condense out of nebular material, forming the sun and the solar system.
500 million years ago The Kikiroy Empire flourished. (25A computer entry)
50,000 years ago Commissioner Bele of the planet Cheron begins his pursuit of the political dissident Lokai, who was wanted for treason and attempting to lead a revolution against the planet's government. ("Let That Be Your Last Battlefield" [TOS])
20,000 years ago A civilization flourished on the planet Zamphor, in the Digifal system. A member of this nearly immortal civilization is believed to have impersonated the Earth deity Quetzecoatl nearly 20,000 years later. ("The Feathered Serpent" [25A])
Thousands of years ago The Nauians of Pollux V put themselves into suspended animation to escape from an ice age. ("Demon World" [25A])
c. 400 B.C. Members of an alien race from the Sahndara system visit Earth after their sun went nova, they stayed in the Greek Empire and became followers of the philosopher Plato. The aliens decided to call themselves the Platonians, and when the Greek Empire ended, the Platonians went to live on another planet which they renamed Platonius. ("Plato's Stepchildren" [TOS])
c. 200 A.D. The inhabitants of Vulcan engaged in terrible and destructive wars, a result of the violent passions and emotions that governed the Vulcan people. The philosopher Surak leads the Vulcans on the path toward logic and peace. However, Vulcan dissidents who still clung to their warrior ways left their homeworld to found what became the Romulan Star Empire. ("The Savage Curtain" [TOS])
c. 800 Klingon warrior Kahless the Unforgettable unites the Klingon Homeworld and provides his people with the laws of honour. ("The Savage Curtain" [TOS])
12th Century to 16th Century The Aztec civilization flourished on Earth. The Aztecs were heavily influenced by the teachings of Quetzecoatl, who was actually a nearly immortal alien being. ("The Feathered Serpent" [25A])
c. 1200 The Lucrs and the Sofs on the planet Proxtrey engage in a nuclear war. Their civilization suffer such severe damage such that by 2268 they still have not regained space capability. Scythe, the moon of Proxtrey, was hurled into a solar orbit as a result of the war. ("That Old Devil Moon" [25A])
16th Century The Aztec civilization on Earth was destroyed by European military conquerors, most notably by the Spanish conquistador Cortez. ("The Feathered Serpent" [25A])
1992 A genetically engineered dictator, Khan Noonien Singh, rises to power and eventually assumes control over one quarter of the Earth. ("Space Seed" [TOS])
1993 A group of genetically engineered "supermen" seize power in 40 of Earth's nations, leading to a series of terrible wars known as the Eugenics Wars. ("Space Seed" [TOS])
1996 The Eugenics Wars end when Khan Noonien Singh is overthrown. Khan and his followers escapes from Earth on the sleeper ship SS Botany Bay. ("Space Seed" [TOS])
2053 Earth's civilization is devastated by World War III. The infamous Colonel Green is a key figure in this horrific conflict, which results in over 600 million casualties. Earth's climate experiences a serious "nuclear winter" caused by thousands of tons of dust and debris kicked into the atmosphere by nuclear explosions. ("The Savage Curtain" [TOS]) and (ST:FC)
2063 Zefram Cochrane pilots Earth's first faster-than-light spaceflight. The warp signature of Cochrane's spacecraft, the Phoenix, attracts the attention of a passing Vulcan ship, which then makes first contact with the people of Earth. (ST:FC) T'Pau of Vulcan was present at the first contact. (25A and JR computer entries)
2065 Earth vessel SS Valiant embarks on an exploratory mission. It encounters the galactic barrier at the edge of the Milky Way Galaxy, and is destroyed shortly thereafter. ("Where No Man Has gone Before" [TOS])
2067 Earth colony ship SS Conestoga leaves for Terra Nova, marking the beginning of Earth's colonization of deep space. By this time, New Berlin was already built on the Moon, Utopia Planitia on Mars, as well as several asteroid colonies. ("Terra Nova" [ENT]) See 2103.
2103 Earth's colonization of Mars begin. ("The 37's" [VOY]) Curiously, "Terra Nova" [ENT] established that Utopia Planitia (unknown whether it refers to some facility or colony) was already built by 2067. Perhaps this entry refers to some other large-scale colonization of Mars.
2119 The Three Systems Wars between the Vurians and the Antoshi results in the extermination of the Vurians. ("Voids" [JR])
2148 The Gadani system goes supernova. (25A computer entry)
2151 First contact between Humans and Klingons take place when a Klingon ship crash-lands on Earth, and Earth returns the sole survivor to the Klingon Homeworld. ("Broken Bow" [ENT])
2151 Earth starship Enterprise NX-01 is launched under the command of Captain Jonathan Archer. It is the first starship built by Humans to achieve warp 5. Its first mission was to return the Klingon survivor to the Klingon Homeworld. ("Broken Bow" [ENT])
2152 First contact between Humans and Romulans take place when the Enterprise NX-01 struck a cloaked mine in Romulan space and was escorted away by Romulan vessels. ("Minefield" [ENT])
2152 First contact between Humans and Tholians take place when the Enterprise NX-01 and several Tholian vessels battled each other in order to secure a time pod from the future. ("Future Tense" [ENT])
2160 The Earth-Romulan War which has been fought with atomic weapons ends with the Battle of Cheron. A neutral zone is set up separating Terran and Romulan space. At this time, Humans have no knowledge of Romulan physiology and history. The treaty is negotiated via subspace radio. ("Balance of Terror" [TOS]) As a result of the war, Centurius III, a former Human colony, was rendered uninhabitable due to radiation levels. (25A computer entry)
2161 The United Federation of Planets is established.
2165 Sarek of Vulcan is born. ("Journey to Babel" [TOS])
c. 2169 A Klingon-Romulan war results in the destruction of the Klingon colony Zhraad. (JR computer entry)
2198 An illness caused by infection of mutated harmless alien bacteria is brought aboard a space tug. It is later named Nuigaireyn Disease. ("Demon World" [25A])
c. 2198 The Demiri Pirate Clan of Menalvagor adopt the name "ajElasi" as their surname. (25A computer entry)
2208 The worst violation of the Prime Directive takes place with the Galahad Incident in which, the USS Galahad intervened in a civil war on Shiva Omicron IV, resulting in the extermination of the Jerion race. Captain Joshua Mulroney Grant was court-martialed for his actions. (25A computer entry)
2218 Brightstar III is settled by the Interstellar Mining and Development Corporation (IMDC).(JR computer entry)
2220 Garth Tyler is born on New Sparta, Mars. (JR computer entry)
2243 Dr. Richard Daystrom invents duotronic computer technology and is award the Nobel and Zee-Magnees prizes. His revolutionary systems become the basis for the main computers used aboard the USS Enterprise. ("The Ultimate Computer" [TOS])
2245 Federation starship USS Enterprise NCC-1701 is launched from the San Francisco Yards orbiting around Earth. (Conjecture)
2245-2250 USS Enterprise's five-year mission of exploration under the command of Captain Robert T. April. (Conjecture)
2250 Captain Christopher Pike assumes command of the USS Enterprise. (Conjecture)
2251-2256 USS Enterprise's first five-year mission of exploration under the command of Captain Christopher Pike. (Conjecture)
2256-2257 USS Enterprise undergoes a year of refit work in spacedock. (Conjecture)
2256 Brightstar III becomes renowned as a fledging artist colony supported by the IMDC. (JR computer entry)
2257-2261 USS Enterprise's second five-year mission of exploration under the command of Captain Christopher Pike. (Conjecture)
2257 A blood draining cloud known as the cumulo-haevus kills 200 crewmen aboad the USS Farragut near Tycho IV. Lieutenant James T. Kirk was one of the few survivors from the attack. ("Obsession" [TOS])
2258 The "sav-a-ship" life support units were extensively used on small ships and bases. (25A computer entry)
2258 Lieutenant James T. Kirk of the USS Farragut exposes Vardaine scientist Dr. Ies Breddell's scheme to overthrow the Vardaine Council, resulting in Breddell's dismissal from the Vardaine Science Council. ("Vengeance" [25A]) Kirk was helped by Vardaine official Vakada Sheme. ("Federation" [JR])
2260 Antonia Gruen graduates from Starfleet Academy. (25A computer entry)
2260 Vardaine official Vakada Sheme is executed for attempting to expose a covert Vardaine Constitution-class starship building program to the Federation. ("Federation" [JR])
2261 USS Enterprise undergoes a major refit at spacedock (Conjecture)
2263 Dr. Marius Tinka is diagnosed with brain tumour and he undergoes treatment. (25A computer entry)
2263 The Kelver Uprising occur on Rigil VII. Thousand of Federation hostages were taken.The hostages later managed to free themselves and negotiate a truce between the Kelver and the Rigilian Government. Starfleet officer Walter Ellis was present during the uprising. (JR computer entry)
2263 The USS Constitution embarks on a five-year mission under the command of Commodore Jake Aldrin. (25A computer entry)
2263 James T. Kirk is promoted to Captain of the USS Enterprise. (Conjecture)
2264 The USS Enterprise embarks on a five-year mission of exploration under the command of Captain James T. Kirk. (Conjecture)
2264-2265 USS Enterprise's first year of exploration under Captain James T. Kirk.
2265 The USS Enterprise encounters an ancient recorder buoy later determined to be from the SS Valiant. ("Where No Man Has Gone Before" [TOS])
2265-2266 USS Enterprise's second year of exploration under Captain James T. Kirk.
2266 Captain Antonia Gruen assumes command of the USS Halsey. (25A computer entry)
2266-2267 USS Enterprise's third year of exploration under Captain James T. Kirk. (TOS Season 1)
2267 The USS Enterprise encounters the sleeper ship SS Botany Bay and revives its crew, including Khan Noonien Singh. Khan and his followers were later marooned on Ceti Alpha V after they fail to hijack the Enterprise. ("Space Seed" [TOS])
2267 The Organia Crisis nearly brings the Federation and the Klingon Empire into war. War was averted when the Organians impose the Organian Peace Treaty on both sides. ("Errand of Mercy" [TOS])
2267 The USS Enterprise investigates a space-time distortion phenomenon, later discovered to be a sentient time portal known as the Guardian of Forever. ("The City on the Edge of Forever" [TOS])
2267-2268 USS Enterprise's fourth year of exploration under Captain James T. Kirk. (TOS Season 2)
2267 A weapon known as the Planet Killer destroys solar systems L-370 and L-374, and threatened several Federation colonies before it was destroyed by the efforts of the crew of the USS Enterprise. The USS Constellation was destroyed during the attempt to stop the weapon. ("The Doomsday Machine" [TOS])
2267 The Babel Conference takes place to decide about Coridan's admission into the Federation. ("Journey to Babel" [TOS])
2267 The Romulan, Klingon and Federation governments, in a joint venture, establish a colony on Nimbus III, dubbing it the "Planet of Galactic Peace". The experiment would eventually fail. (ST5)
2268 The Klingon Empire and Romulan Star Empire enter into an alliance which involve a sharing of military technology and spacecraft designs. Well, this has to occur before 25A since the Romulans were already seen using starships of Klingon design in 25A.
2268 The events of 25A takes place. There is a possible paradox since the 25A computer entries contain information on the Zetars and Excalbia (see 2269).
2268-2269 USS Enterprise's fifth year of exploration under Captain James T. Kirk.. (TOS Season 3)
2268 The USS Enterprise, at the planet Triacus, discovers all adult members of the Starnes Expedition to have been killed by an evil entity which called itself the Gorgan. The Gorgan attempted to gain control of the Enterprise but was destroyed before it could do so. ("And the Children Shall Lead" [TOS])
2269 Energy beings known as the Zetars attack the Federation archive on the planetoid Memory Alpha and cause severe damage to the facility. ("The Lights of Zetar" [TOS])
2269 The USS Enterprise makes contact with the Excalbians on the planet Excalbia. ("The Savage Curtain" [TOS])
2269 The events of JR takes place.
Eons ago An alien being that would one day be known as the cosmic entity, the Savant, sheds its physical form to become a being of pure emotion. ("Voids" [JR]) Probably less than 15 billion years ago.
More than 10,000 years ago The Brassica last visit the planet Onyius II. ("Light and Darkness" [JR]) According to Spock's deduction, the Brassica left Onyius II before Humans left the Cro-Magnon stage of development, which was between 40,000 and 10,000 years ago.
Centuries ago The Andorians colonise the planet Menalvagor in the Elasi Prime system. Conflict will eventually arise between the native Elasi and the Andorian colonists, leading to Elasi pirate attacks against the Federation. (25A computer entry) This took place before the Andorians' entry into the Federation. The Federation was established in 2161, so the Andorians could have joined the Federation only on or after this date. The Andorians were already Federation members by the time of the Babel Conference (2268). Therefore, the Andorian colonization of Menalvagor took place centuries before sometime between 2161 and 2268, but I'm not sure exactly when.
Sometime in the late 22nd Century A group of isolationist Humans colonise the planet Harlequin III, which later became known as Vardaine. Although Vardaine would join the Federation, the Vardaine people would continue to remain reclusive, even by the year 2268. (25A computer entry)
Sometime in the 23rd Century The Mars colonies were threatened by imperial Earth interests during the Declaration Crisis. During this crisis, a Constitution-class starship, the USS Olympus Mons, served as the flagship for the Mars colonists and defended the Mars colonies. (JR computer entry) This has to occur sometime after the colonization of Mars began (in 2103), and it has to be fairly recent, since the Olympus Mons was a Constitution-class starship. It was not stated what the Declaration Crisis was all about, although I suspect that it was a declaration of independence by the Mars colonies.
Recently Tergen III was evacuated when the Tergen star entered its expansion phase of its cycle. Tergen immigrants to Vardaine were allegedly pressed into cheap labour, in violation of their sentient rights. This subsequently prompted a Federation investigation. (25A computer entry) Obviously, this has to occur sometime after 2161 (establishment of the Federation), and after the colonization of Vardaine in the late 22nd Century.