Star Wars: Timelines dates the events of "Brain Invaders," in which the second occupation of Geonosis starts, to 21 BBY. Dawn of Rebellion specifies that the Empire continued to hold its presence on Geonosis until the sterilization of Geonosis, which is dated to circa 9 BBY by Star Wars: Timelines.
Usage
{{SecondoccupationofGeonosisdate}}