Bak Full Moon Poya Day is a National Holiday in Sri Lanka. It usually falls in April. This Poya commemorates the second visit of the Supreme Buddha to Sri Lanka in the fifth year of his Supreme Enlightenment. According to the ancient chronicles of the Mahavamsa, he saw a hostile atmosphere between the two factions of the Naga community and went to Nagadipa. On this journey, the goddess Samadhisumana came with the Blessed One.
There were two factions of the Naga tribe. One group was led by King Mahodara, the ruler of the Naga kingdom. He married his sister to the ruler of the hills of Kannavadamane and they had a son named Chulodara. He was the Leader of the Opposition. It was a war between uncle and son-in-law and they fought on the gem throne called Manipalaga. It was given to Chulodara’s mother by her father.
When the Lord Buddha came to that place by his divine power, the two warring parties were on the battlefield. Using this power, he covered the whole area with darkness and then filled it with bright light. When the members of the Naga tribe saw this miraculous deed, they joyfully worshiped the Buddha. He then told folk tales or jathaka katha to preach his message. These were the Kakoluka, Phandana, Latuka, and Wattaka Jataka Stories from the Pansiyapanas Jathaka Pothvahanse which put across a message of peace and harmony. In this way, he was able to bring about unity among the Naga people.