I noticed the last couple of years Sri Guru Nanak Dev Jis joti jot is always on September 22nd. Whoever selects these dates what source/sources are they using? I'm assuming they are using Bhai Balas Janam Sakhi and Bansvalinama since Guru Sahibs joti jot is written as Asu Vadi 10 ( which is equivalent to September 26), but JanamSakhis only give dates of Pelhi Paatshaah. Does this mean all other dates come mainly from Bansvalinama?
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥