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.
It is time for GRAND MOFF TARKIN to repay a long-standing debt to DARTH VADER…and settling what is owed will require every last bit of his cunning, and will cost more than he ever imagined.