King Kansa of Mathura received a prophecy that his sister Devaki's eighth child would kill him. His response was to imprison Devaki and her husband Vasudeva and kill each child born to them. Seven children died this way. When the eighth child — Krishna — was born at midnight, something extraordinary happened: the guards fell asleep, the prison doors opened on their own, and Vasudeva carried the newborn across the flooded Yamuna river to Gokul, where he placed him in the care of Yashoda and Nanda. A girl child born to Yashoda that same night was carried back in his place. When Kansa tried to kill this child, she slipped from his hands, flew into the sky, and declared that his destroyer had already been born.

Krishna grew up in Vrindavan — a childhood of butter theft, flute music, dancing with the gopis, and defeating a string of demons sent by Kansa. He eventually returned to Mathura and killed Kansa. Then came Kurukshetra, the Mahabharata, and the Bhagavad Gita — spoken to Arjuna on a battlefield as both armies stood ready.

In Bengal, the relationship with Krishna was transformed by Chaitanya Mahaprabhu (1486–1534). Chaitanya's movement — Gaudiya Vaishnavism — shifted the focus from Krishna the warrior and king to Krishna the beloved: the young man of Vrindavan who plays the flute and makes Radha wait. The emotional register of Bengali Krishna worship is almost entirely Chaitanya's inheritance. Kirtan, the Radha-Krishna relationship, the intensity of bhakti as love rather than duty — all of this comes through him.

In years where the Ashtami and Rohini don't overlap cleanly, different communities observe the festival on different days. Some go by Ashtami; others wait for Rohini. In 2026, the Bengali panjika will specify which combination applies and what the midnight puja time is.

The fast is strict: no food, no water for many devotees from sunrise until the midnight puja. Children and the elderly often observe a partial fast with fruits. The fast is broken immediately after the birth ceremony at midnight — which is why the midnight prasad is such an anticipated moment.