A calendar system was in use sometime after the Battle of Yavin during the Galactic Civil War that used the pivotal battle as a zero year from which to record galactic history. Dates following the pivotal battle were marked as "ABY" while dates beforehand were marked as "BBY".
The calendar system came into use sometime in the New Republic Era. The calendar was used on a collection of maps thought to have been created by the Ithorian artist Gammit Chond. Various events related to the locations shown were marked on the maps with dates from the calendar included, with many of the events centering on the exploits of the legendary Skywalker family. Chond never visited any of the locations he is thought to have drawn, and was believed to have based the information they contained on travelers' tales, as he never left his homeworld.