Buddhist Lent Day mars the beginning of the annual retreat for monks as laid down by Lord Buddha more than twenty-five centuries ago. On that day all monks take a vow to stay in a particular place or temple for three months from the first Day of the Waning moon in the 8th Month to the 15th Day of the Waxing Moon in the 11th Month. It coincides with the rainy season during which the monks are not allowed to stay overnight anywhere else, except in exceptional cases based on reasons granted by Lord Buddha.

Buddhist Lent day means the day on which the Buddhist monks take the vow to stay only at one particular place or temple which can shelter them from the sun, storms and rain.