Poson is a festival celebrated in Sri Lanka on the full moon day in June. Poson Poya is noteworthy to Sri Lankan Buddhists as the day on which Emperor Asoka's son, Arahant Mahinda, introduced Buddhism to the island in the 3rd century B.C.
Vesak falls in May in every year and it is considered as the largest poya in Sri lanka. It is considered as a cultural as well as religious festival. Other than Sri Lanka, Asian countries like India, Japan, Singapore, Taiwan, Indonesia and Nepal celebrate Vesak poya in grand way. Not only is that It now considered as an international holiday.
Bak Full Moon Poya Day is on the Full moon day of April. This is noteworthy, as Bak is a month of national importance as well. This holy day celebrates the second visit of the Buddha to Sri Lanka, which took place in the fifth year of his supreme enlightenment in order to reconcile two local chiefs, Mahodara and Chulodara, uncle and nephew, who had fallen into disagreement and were threatening hostility over a throne beset with jewels. The theme of the day is Right Understanding (Samma Ditthi).
Navam full moon has special significance for the Buddhists in Sri Lanka and in the world. The two very significant incidents that took place on the Navam Pura Pasalosvaka Poya Day were the first ever Buddhist congregation and the appointment of two chief disciples of Gautama Buddha as Aggasavakes namely Sariputta and Moggallana. In the eve of the first Navam Full Moon Poya day after the Enlightenment of Gauthama Buddha, there were more than One thousand two hundred and fifty disciples in the Order of Maha Sangha.