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 possibility-and destruction-of the Death Star has changed everything. The Death Star's destruction proves the Empire is not irresistible. But a Death Star has been built, and it can't happen again. The specter of the Empire's true power has brought together a patchwork cloth of people, united in hope. From the desolation of Jedha to the search for new bases, these rebels continue to fight for a better tomorrow for a galaxy far, far away in these all-new adventure written by Kieron Gillen (DARTH VADER, DOCTOR APHRA).