According to the chronicle, on this full moon day, Buddha first visited Sri Lanka during the first year of The Buddha's Enlightenment.. During the time of the Buddha’s first visit, Yakkhas who were humans and descendents of Rawana and his brother Vibhhishana inhabited in Sri Lanka. The Buddha knew that Sri Lanka would become the stronghold of Buddhism in the future.

On Duruthu Full Moon Day the Yakkas gathered for a meeting at a riverbank where the Mahiyangana Dagoba was built in a later time. The Buddha stood in the sky above Mahanaga Grove where the Yakkhas were meeting. The Buddha stood there radiating rays of light from his body more pleasant, clear, calm and gentle than the moonlight. A rainbow-like halo emanated around Buddha. The Buddha gave a clear message to the inhabitants of the country and advised them to live and follow the five precepts, Even the Devas attended this gathering.

Sumana of Samanthakuta attained the first stream enterer (Sowan). He begged for a memento to worship. The Buddha gave him few of his hair, which the Deva enshrined at Mahiyangana. This happened to be the first Stupa to be built in Sri Lanka.