Aatham" ,"Gokulashtami", "Ashtami Rohini", "Srikrishna Jayanti", "Sree Jayanthi" or sometimes merely as "Janmashtami", is a Hindu festival celebrating the birth of Lord Krishna , an avatar of god Vishnu . Krishna Janmashtami is observed on the eighth day, Ashtami tithi , of the dark half or Krishna Paksha of the month