Bak full moon day commemorate the second visit of the Buddha to Sri Lanka in the fifth year of his Enlightenment. This visit was to save two local chiefs Mahodara and Chulodara threatening to start a war to claim the jewel-beset throne. At first the Buddha hovered above them and called forth darkness over the battlefield. This terrified the Nagas, and the Buddha comforted them. They all worshipped him and offered their throne. The Buddha sat onf the throne and preached Dhamma and converted them to be his deciples.

The Naga King of Kalyani, Maniakkitha invited the Buddha to visit Kelaniya. The Buddha accepted the invitation and returned to Jethavanaramaya.