BBY/ABY is used to position items along the Star Wars Timeline. BBY refers to Before the Battle of Yavin. ABY refers to After the Battle of Yavin. The Battle of Yavin in Episode IV: A New Hope occured in 0 BBY/ABY.
The planet Shu-Torin, (introduced in the Darth Vader Annual), is revolting. Darth Vader is tasked with leading a military assault. Has Vader's rise to glory begun?