Janmashtami is the birthday of Lord Krishna. Krishna Janmashtami is observed on the eighth day of the dark half of the month of Bhadrapada in the Hindu calendar , when the Rohini Nakshatram is ascendent. The Hindu calendar being lunar, these two events [the day being the eighth of the waning moon and the Rohini Nakshatram being ascendent] may overlap for only a few hours. Read more about Janmashtami>>