Songkran, 13 April

Songkran falls on the thirteenth of April by the traditional reckoning this rule records, marking the Thai New Year and fixed historically by the movement of the sun into the astrological sign of Aries in the traditional solar calendar shared across much of mainland Southeast Asia's Theravada Buddhist societies, rather than by a lunar or lunisolar system of the kind that governs the Hebrew or Islamic calendars. The same solar transition and roughly the same mid April date are marked under different names in neighboring countries sharing the same Theravada Buddhist calendrical tradition, Thingyan in Myanmar, Choul Chnam Thmey in Cambodia, and Pi Mai Lao in Laos.

Religious practice on the day includes bathing images of the Buddha and offering food to monks, acts of purification that the festival's much more visible public water throwing, splashing water on family, neighbors and strangers alike as a symbolic washing away of the past year's misfortune, is widely understood to have grown outward from. The water throwing has become the festival's dominant public image internationally, drawing large numbers of visitors to Thailand specifically for it, even as the religious observances at temples that give the festival its original devotional content continue alongside the more visible street celebration.