Star Wars Timekeeping - ABY and BBY

How to Decode Dates in the Star Wars Universe

Battle of Yavin
Rebel X-wing starfighters fly past the planet Yavin on their way to battle the Death Star. Lucasfilm Ltd.

When you are exploring the universe of Star Wars, you'll encounter dates listed as BBY and ABY and you may wonder what they mean. ABY stands for "After the Battle of Yavin," while BBY stands for "Before the Battle of Yavin." As with the birth of Christ and dates being designated B.C. and A.D. in Western cultures, this battle was so significant that they use it as the ultimate demarcation of events, the "year everything changed."

What Happened in the Battle of Yavin?

In the Battle of Yavin, which took place at the end of "A New Hope," the Rebel Alliance destroyed the First Death Star near the rebel base on Yavin 4. This marked one of the first major successes for the Rebel Alliance and foreshadowed the downfall of the Empire. Aided by a flaw designed into the Death Star by a rebel, heroes Luke Skywalker, Wedge Antilles, Han Solo, and the Force ghost of Obi-Wan Kenobi were able to destroy the Death Star. Skywalker and Solo were presented medals of honor by Princess Leia Organa for their courage. Nemesis Darth Vader narrowly escaped in the attack.

First Use of BBY and ABY for Star Wars Dates

The terms ABY and BBY were first used by fans as a convenient dating system for events in the Expanded Universe. The Battle of Yavin takes place in 0 BBY, with years before it (BBY) counted backward and years after it (ABY) counted forward, just like dates in B.C. and A.D.

In-Universe Uses of BBY and ABY

The BBY/ABY system was used by the New Republic, the government formed by the Rebel Alliance after they overthrew the Empire. Other cultures and political entities had their own calendars based on important events. For example, some Jedi historians used the terms BTC and ATC to refer to years before and after the Treaty of Coruscant, which ended the Great Galactic War in 3,653 BBY.

The Galactic Standard Calendar

The standard measurement of time in the Star Wars universe if the Galactic Standard Calendar, based on the Coruscant tropical year, which is 368 days long. In this calendar, the universe came into existence 13 billion years BBY. The Pre-Republic Era lasted until 25,053 BBY, with the Rakata using the Dark Side of the Force and the dawn of the Jedi in 46,453 BBY.

The Old Republic was established in 25,053 and the Jedi served as the guardians of peace and justice. By 1000 BBY the republic had become too corrupt and unwieldy, making it ripe for intrigue. Darth Sidious, a Sith Lord, was able to rise secretly to Supreme Chancellor and kill most of Jedi. The events of "The Phantom Menace" occur in 32 BBY, "Attack of the Clones" in 22 BBY, and "Revenge of the Sith" in 19 BBY.

The era of The Rebellion was from 0 BBY to 4 ABY. "A New Hope" is, of course, in 0 BBY, as are the events in "Rogue One." "The Empire Strikes Back" is in 3 ABY, and "Return of the Jedi" is in 4 ABY. It was followed by The New Republic era from 4 ABY to 25 ABY. During this era, Luke Skywalker trains new Jedi to restore the order, growing it to over 100 knights.

The New Jedi Order era is from 25 ABY to 40 ABY. "The Force Awakens" is set approximately 30 ABY. Further epochs explored in the Star Wars universe include the Legacy era of 40 ABY to 140 ABY.