The Golden Age was the 600-year period of peace and prosperity in the galaxy following the great unrest of the Jedi Rebellion and the following incorporation of remaining entities into the Galactic Empire. During this time, the Imperial Order of the Sith filled in the void previously occupied by the Jedi.
The Golden Age lasted for the 600 years between 400 NE and 1000 NE
Previous era: Galactic Unification
Following era: Millennial