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 Clone Wars
Now that Anakin Skywalker is a full-fledged Jedi Knight, his days of being a Padawan learner are behind him. But the Jedi Council has assigned him a Padawan of his own. Her name is Ahsoka, and this young girl just might be more than the Jedi can handle.