I'll call it:
From 2013 to the nightmare universe of the 41st millennium, or... how the hell did we get from here to there?
2013- 20th millennium
Little is known about this period of time. It is variously called the Golden Age of Technology, the Dark Age of Technology or simply the time before Old Night. What can be assumed is that mankind developed countless awe-inspiring technologies that allowed them to colonize millions of worlds.
Chief amongst this tech was the Standard Template Construct (STC) which allowed colonists access to all the technology mankind had developed using whatever materials were locally available (think of it like a replicator from Star Trek the Next Generation).
At some point during this time humans discovered another dimension parallel to ours called the Immaterium, the Ether, or most commonly it is referred to as the Warp or Warp Space.
Warp Space is a realm of pure energy that does not conform to the laws of physics. Man developed warp drive that formed a tear between the two realms that would allow ships to travel into Warp Space and since physics and time mean nothing in this realm, massive distances could be travelled in a short span of time.
A ship emerging from the Warp
If it had stayed that way then man might have become the kings of the universe.
But that was not to be...
Tune in tomorrow for part two- The Coming of Old Night