Vap Full Moon Day, commemorate several significant events. Seven years after the Buddha’s enlightenment, he visited Thavathinsa Heaven to preach Abhidhamma to Mathru Deva sitting on Sakra’s throne. He spent the whole Vassana season there and returned directly to Sankassa on Vap full moon day.

On a Vap Full Moon day the Buddha  declared Arahat Sariputta as the most intelligent of all Arahants and among all the disciples.

The King Devanampiyatissa sent a royal diplomatic delegation headed by his Foreign Affairs Minister Aritta to meet Emperor Asoka requesting him to send his daughter Sanghamitta Theri to Sri Lanka to establish the Bhikkhuni Sasana (Order of Nuns).

From the Esala Full Moon Day to Vap Full Moon Day the rain-retreat period where the Buddhist monks remain indoors or in their monasteries. This is the last month of the rainy season. Full activities of preaching recommence after the Maha Pavarana on this Full Moon day. The Vap Full Moon  Day is also known as the Cheevara Masaya or period of Katina.

It was on a Vap full moon Day the first Sinhala Arahat - Mahaaritta Thera, held Buddhist Council to Bhikkus at Thuparama Temple in Anuradhapura.