Since Sri Lanka is predominantly Buddhist country, Buddhist festivals are more frequent. In fact, full moon day of every month is regarded as a religious observance for the Buddhists; it is called Poya Day. However, the main full moon days reminiscent to the religious important events are :-
Duruthu Perahera :- Held on the poya day in January at the Kelanyia Raja Maha Vihara in Colombo and second in importance only to the huge Kandy perahera, this festival celebrates a visit by the Buddha to Sri Lanka.
Vesak :- This full moon day is a day of the great significant for the Buddhists around the world for it marks the Birth, Enlightenment, and Decease of the Buddha. The Buddhist houses on the island are decorated with bright Vesak lanterns. The alms halls offer free meals to passer-by and Buddhists go to temples or shrines for religious observance.
Poson Poya :- The Poson full-moon day in june is a celebration of the bringing of Buddhism to Sri Lanka by Mahinda. Anuradhapura and Mihintale, where Mahinda met and converted the Sinhlse king, are the main sites for the elebration. On this day thousands of white-clad piligrims climb the stairs to the summit of Mihintale.
Kandy Esala Perahera :- The Kandu Esala Perahera, the most important and spectaular festival in Sri Lanka, is the Climax of 10 days and nights during the month of Esala, ending on the Nikini full moon. This great procession honours the scared Tooth Relic of Kandy. Smaller peraheras are held at other locations around the island.
Vel :- This festival is held in Jaffna and Colombo. The gilded chariot of Skanda(or Murugan), the God of war, complete with this vel (trident), is ceremonially hauled from a temple has a 25-day festival in honour of Skanda/Murugan.