After the Treaty of Coruscant, the Galactic Senate adjusted the dates on the time system to correspond to BTC (Before the Treaty of Coruscant) and ATC (After the Treaty of Coruscant).
The Treaty of Coruscant happened 3,653 years before the Battle of Yavin, so in the standard Star Wars calendar it would be 3,653 BBY.
The Knights of the Old Republic game is set in 303 BTC.
The Knights of the Old Republic II is set in 298 BTC.
Star Wars The Old Republic is set in 9 ATC.