Khao Phansa is a Buddhist holiday, which is observed on July 09, 2017. Due to the lunisolar calendar the date varies from year to year in the Gregorian solar calendar. It is tradition that has been practiced primarily by the Theravada Buddhist. Khao Phansa initiates the three-month rainy season, during which Buddhist monks stay in their monastery or temple and leave only if it is absolutely necessary.
According to the legend, it was already in Buddha's time tradition for Buddhists to remain in the temples and monasteries while Vassa, as the rainy season is also known, and to concentrate on the essentials. Background of this tradition was to protect budding plants. To minimize the danger of accidentally destroying vital plants while hiking, the monks retreat for this time. This goes so far that they leave the monastery only in absolute emergencies and are not allowed to spend more than seven consecutive nights outside the monastery.