Poson, held on the full moon day of June, commemorates the occasion over 2,000 years ago when Arahat Mahinda, son of Emperor Asoka of India, converted King Devanampiyatissa to Buddhism.

The main centre of celebration is Mihintale, the ancient monastic complex where the mission headed by the Arahant Mahinda included Itthiya, Utthiya, Sambala and Bhaddasala Theras perched the first sermon to the ruler King Devanampiyatisa, at Anuradhapura, thereby setting in motion a series of events that eventually made Sri Lanka the home of Theravada Buddhism.

With the establishment of Bhikku Sasanaya, all other elements of a civilized society began to emerge with the art of writing, art, architecture, river civilisation, religious rituals in song and dance forms, literature, all with royal patronage.

For Buddhists, this hallowed day of Poson is second only to Vesak in terms of importance.