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.
A stylized retelling with stickers of how Luke Skywalker met R2-D2, C-3PO, and Obi-Wan Kenobi in Star Wars: A New Hope.