Janmashtami, the birth of Lord Krishna is celebrated with great devotion in the August/September months.
The ceremony of worship is a very simple affair. The priests chant holy mantras and bathe the idol with Gangajal (water from the holy Ganges river), milk, ghee (clarified butter), oil, and honey pouring all these from a conch shell. Only after the ceremony is over, the devotees break their daylong fast . In Janmashtami, the devotees keep awake and sing bhajans till midnight, the moment when Krishna was born. People fast all day and eat only after the midnight birth ceremony. Often the image of the baby Krishna is placed on a swing and bathed with charanamrit (holy water). Midnight prayers are performed. The sound of hymns and religious songs extol the greatness of Krishna.
This festival occurs on the eight day (Astami) of a lunar fortnight hence the name (Krishna+astami). Krishnastami which comes sometime in August is celebrated over two days. The first day is Krishnastami or Gokulastami. The second day is called Kalastami or more popularly Janmastami.