According to Wookieepedia, the Battle of Malachor V took place in 3,960 BBY, and Revan and Malak returned in 3,959 BBY, a year later.. But everything with the mandalorians was probably not over when the Battle of Malachor ended, so you have to add some time to that, and the Jedi Council probably had a debate on what to do with the exile, so that could explain why there's a year of delay... But it surely was after Revan returned to known space, the Jedi on the Council speak of Revan and how they can't be vulnerable on two fronts.