Guru Maharaj: When Devaki, after Krishna in the wrestling match, He killed Kamsa, Devaki and Vasudeva first were offering their obeisances. Then Krishna sprinkled some lila dust on them. And then they said, oh, my dear son, took Him on the lap! And Vasudeva embraced Balarama and Krishna. So, they were so happy. At that time, He was asked when were You born and when to observe the Krishna Janamastami? Then He said, that I appeared on the dark ashtami of Sravana month and you can observe it that. Everybody was observing it in Mathura. Haribol!