From Lexicanum

Year	Event	Source
M22	The development of the navigator gene allows human pilots called Navigators to make longer and faster 'jumps' through the Warp than was previously thought possible. The great Navigator families, initially controlled by industrial and trading cartels, gradually become power bases in their own right. Humanity continues to explore and colonise the galaxy, while the human worlds politically unite and a golden age of scientific achievement begins. Non-aggression pacts are signed between humanity and dozen of alien races. Perfection of the Standard Template Construct (STC) system allows an almost explosive Human expansion to the stars. This Golden Age of Mankind continues until M25.	Warhammer 40,000: Rogue Trader, Space Marine by Ian Watson, Galaxy in Flames page 410 by Ben Counter

M21	Timeline	M23