4th century

An atomic bomb detonates on Vulcan

The 4th century is defined by the calendar of Earth as occurring from the year 301 through the year 400.

Events

The inhabitants of Vulcan engage in terrible and destructive wars including the use of atomic bombs, a result of the violent passions and emotions that govern the Vulcan people. It is a savage time, even by Earth standards. Myths from this period describe a terrifying weapon of war called the Stone of Gol that kills with the power of the mind. (TOS: "Balance of Terror", "Amok Time", "All Our Yesterdays"; TNG: "Gambit, Part II"; ENT: "Awakening")

The Time of Awakening: Surak of Vulcan leads his people onto a path of peace and logic. (TOS: "Amok Time", "The Savage Curtain"; TNG: "Gambit, Part II"; ENT: "Awakening")

A group of Vulcans who do not follow Surak's teachings of logic leave their homeworld in a wave of emigration. They will finally settle on the planets Romulus and Remus, coming to be known as the Romulans. (TOS: "Balance of Terror", "The Enterprise Incident"; TNG: "Unification II", "Gambit, Part II")

The Debrune, an offshoot of the Romulans, establish an outpost on Barradas III. (TNG: "Gambit, Part I")

It is possible Calder II, Dessica II, Draken IV, and Yadalla Prime were also associated with the Debrune or other early Romulans.

The Vidiian Sodality in the Delta Quadrant is ravaged by a deadly viral disease called the Phage. The Vidiians survive only by harvesting organs from non-Vidiians to replace their own tissues. (VOY: "Phage")

According to Star Trek: Star Charts, Vulcans became warp capable in 320 AD. However, according to known accounts, the Vulcans invented warp drive some time after 1947. (DS9: "Little Green Men") On the other hand, according to a story told by T'Pol, a Vulcan survey ship observed the launch of Sputnik in 1957, which would be quite early, if the Vulcan warp drive was developed after 1947. (ENT: "Carbon Creek") It was also established that the Vulcans took "a hundred years" to go to warp 2, so First Contact in 2063 would have been quite early, too. (ENT: "First Flight")