13,000,000,000 BBY: The Big Bang, the galaxy is formed.

According to most sources, the galaxy was 120,000 light years across, and had a supermassive black hole at its core. The galaxy was orbited by 7 satellite galaxies (Aurek, Besh, Cresh, Dorn, Esk, Forn, and Grek), most being described as having ancient, metal-rich remnants of stars but little life. A hyperspace disturbance on the perimeter of the galaxy prevented hyperspace travel into extra-galatic space.

5,000,000,000 – 2,000,000 BBY: Life emerges



In this period of time, over 180 billion stars had formed planets that could support life. 10% eventually developed life, while intelligent life formed on 1/1,000 of these worlds. It was estimated that only 1 billion systems were eventually populated. These populations consisted of a wide array of creatures such as the Gorothites, Chevin, pre-arboreal Wookiees and many many others.

2,000,000 BBY: The Oracle is built on the world of Pelgrin



An ancient and mysterious construct, the Oracle is perhaps one of the oldest artifacts known to civilization. It was located within a housing made of Dieuw tree wood and unknown metals, and stood over ten stories high. It possessed a complex mechanical network consisting of gears, switches, and pendulums.

200,000 BBY: The Battle of Notron (Later known as Coruscant)



The Zhell, early ancestors of humans, vie for control of their home world with the Taung, a warrior race that would one day become the infamous Mandalorians. The Zhell organised themselves into 13 Battalions, or the 3 Nations of Zhell to combat the warrior Taung. Sometime during the fighting, a volcanic eruption threw tons of ash into the sky, blocking out the sun, damaging the Zhell fighting capability, and giving the Taung an advantage. Because of this, the Taung adopted the name Dha Werda Verda, or Warriors of Shadow, as an emblem of their destiny. Despite the advantage, the Zhell eventually drove the Taung off world and declared themselves victorious, paving the way for future events to come.

100,000 BBY: The arrival of the Celestials



Around this time, a mysterious race of aliens appeared, who’s actions would ripple through the galactic community and set the stage for the future of all of the galaxies inhabitants. It was in this time that the Celestials used the insectoid Killiks as slave laborers to work on their many projects, such as Centerpoint Station, which in turn was used in the creation of the Corellian system, the Maw black-hole cluster. It is also said that they seeded many of the Core Worlds with life, particularly humans. The Force entity Abeloth is also imprisoned in the Maw black hole cluster by the Celestials during this time.

90,000 BBY: Civilization on Coruscant expands



The metropolis that will eventually be known as Galactic City grows to epic proportions. New levels are built on top of old ones, beginning a trend of upward building that continues for thousands of years.

36,453 BBY: Fall of the Kwa, rise of the Rakata



Around this time, the few remaining Force sensitive Kwa of Tython have died out, and the Kwa as a whole have retreated to their homeworld of Dathomir in fear of the Rakata. Using their Infinity Gate technology, which allowed near-instant travel between various star systems, the Kwa had arrived on the planet Lehon where they discovered the primitive Rakata. Sensing the Rakatans were strong Force-sensitives, the Kwa uplifted them as they had done on many other worlds. Unfortunately, they never saw the true dark nature of the Rakata, which would ultimately spell their demise…

36,453 BBY: Arrival of the Tho Yor, and birth of the Je’daii



Also during this time, eight great pyramid starships, the Tho Yor, activate, calling all Force-sensitives to them. The pilgrims board the Tho Yor, which proceed to acquire Force-sensitives from numerous worlds before traveling to the now vacant Deep Core world of Tython. Not long after, the arrival of the ninth and largest Tho Yor heralds a great Force Storm, which leads to the pilgrims being scattered across Tython. The Tythans soon form the Je’daii Order, a group who strive for balance between the light and dark sides of the Force, known to them as Ashla and Bogan.

35,000 – 25,200 BBY: The Infinite Empire and the Force Wars



Having developed technology pwered by the Dark Side, the Rakatans establish an Infinite Empire spanned over 10 millennia and countless star systems. Shortly before a mysterious plague strips their ability to use the Force, the Rakatans launch an attack on the Je’daii world of Tython. Around the same time, the Force Wars between the Ashla and Bogan began, which resulted in the defeat of the Bogan, and the establishment of the monastic society of guardians known as the Jedi. Many worlds are soon seeded by sublight human sleeper ships, leading to many new colonized worlds. The Rakatan Empire eventually falls due to a galaxy wide revolt of their slaves.

25,130 – 25,096 BBY: Xim the Despot, and beginning of a new Era



Son of the Tionese nobleman, Xer XVIII, Xim takes control of his fathers throne of the Kingdom of Cron and begins a campaign to conquer the Livien Leauge. Over many years and many battles, Xim manages to conquer the Livien Leauge, Tion Cluster, Thanium Worlds, and the Kiirium reaches. Eventually Xim instigates conflicts with the Hutts, sparking a war that lasted many years. After the Second Battle of Vontor, Hutt leader Kossack Inijic Ar’durv convinces the Klatooinians, Nikto, and Vodran to sign the Treaty of Vontor, securing their allegiance. Xim is captured after the Third Battle of Vontor and imprisoned on Varl by Kossack, where he later dies. In that time, a set of Hyperspace beacons are constructed, one known as Belgoth’s Beacon, which sits along the Perlimian Trade route. The end of Xim’s conquest and construction of the beacons marks the beginning of the Expansionist Era.

You can get the comics that explains most of this via amazon below: