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.
Star Wars Legends Epic Collection: The Old Republic Volume 4 is fourth Epic Collection trade paperback collecting Star Wars Legends comics originally printed by Dark Horse Comics in the Old Republic era.