4000

In 4000, the Daleks held a meeting with representatives from seven outer galaxies to plot the invasion and overthrow of human occupied space. (TV: Mission to the Unknown)

Six months later, the First Doctor became involved with the Space Security Service's investigation into the Daleks, Mavic Chen and the Time Destructor. (TV: The Daleks' Master Plan)

After the death of Mavic Chen, a dynasty of his descendants slowly transformed the relatively democratic Galactic Federation into a new incarnation of the old Earth Empire, which had fallen approximately nine hundred years earlier. (PROSE: The Crystal Bucephalus)
 * Most likely, this new empire would become the Second Great and Bountiful Human Empire known to exist by the 42nd century.