Poson, also known as Poson Poya, is an annual festival held by Sri Lankan Buddhists celebrating the arrival of Buddhism in Sri Lanka in the 3rd century BC. The festival is the most important Poya holiday of the year and the second most important Buddhist holiday of the year, being surpassed in importance by Vesak. Poson is celebrated throughout the island, with the most important ceremonies of the festival being held in Anuradhapura and Mihintale. The festival is held in early June, coinciding with the June full moon.