Il Full Moon Poya Day is the last Poya in the rainy season. On Il Full Moon Poya Day was the receipt of permission (Niyatha Vivarana) by Bodhisatra Maitriya to be the next Enlightened One or the Future Buddha Maitriya. Siriwaddana had entered the Buddhist Order as Bhikku Maitriya. The Buddhas with his divine vision and insight predicted that in Benares there will be a kingdom known as “Kethumathi” and a king called Sanka whose advisor Subrahamme and his wife Brahamawathi will be parents of Future Buddha Maitriya and that he will attain enlightenment under Banyan Tree. The prediction of emergence of the future Buddha was announced on Il Full Poya Poya Day.
The Il Full Moon Poya day marks the end of the Rainy Retreat Period or “Vassana-Samaya. The Bhikkus assign themselves to indoors in the temples and observe “Bhavana” meditation and other religious activities in their “Vihara aramayas” Il Poya can be considered as the end and climax of the Rainy Season. The grand ceremonies of offering “Katina Cheeva” can be considered as a highlight of this poya. It is supposed to be one of the higher meritorious acts that individuals can perform. Early morning there are processions carrying the Katina Robe to the temples. Those Buddhist Monks who performed “Pasuvas” (the period after the observance of “Peravas”) terminate the Rainy Retreat period of “Vassana Samaye” on this Il Full Moon Poya Day.
The first stupa in Sri Lanka was called Thupharama in Anuradhaura. The laying of the foundation to construct the Dagaba took place on Il Full Poya Day. The “Aku Dhatu” of Buddha in treasured in this Dagaba.