519 before the Battle of Yavin (BBY) was a year in the chronological period known as the Great Peace of the Republic. During this period, widespread galactic settlement commenced into yet-unexplored regions and the charting of the Deep Core began. This year saw the mass migration of the Kallidahin to the asteroidPolis Massa, where they had already been operating, to discover their possible connections with the extinct Eellayin natives.
↑The New Essential Chronology states that the Ruusan Reformation occurred in 1,000 BBY, which is the zero point of the calendar based on the Ruusan Reformation, so the difference between the calendar based on the Battle of Yavin and the Ruusan Reformation's year-notation system is 1,000 years. This date is derived using simple math based upon other confirmed dates.
↑The New Essential Chronology states that the Ruusan Reformation occurred in 1,000 BBY, which is the zero point of the calendar based on the Ruusan Reformation, so the difference between the calendar based on the Battle of Yavin and the Ruusan Reformation's year-notation system is 1,000 years. This date is derived using simple math based upon other confirmed dates.