Asalha Puja is one of the three most important days of remembrance in Buddhism. It commemorates the first sermon of Gautama Buddha, the Dhammacakkapavattanasutta, which he gave to the (first) group of (five) disciples in Sarnath, India. During this sermon, one of these disciples attained sotapannahood, a degree of holiness. Asalha Puja takes place on the full moon of the month of Asalha, the eighth lunar month of the Hindu lunar calendar. Asalha Puja usually falls in July.
Asalha Puja is the day of the Dhamma because it commemorates the day that the Buddha began to teach the Dhamma, and on that day the first disciple also perceived or realized the Dhamma for himself.
In Buddhist countries such as Thailand, Japan, Tibet, and Sri Lanka, it is one of the most important religious days, and it is a national holiday. On Asalha Puja, the laity gives gifts to the Buddhist temples or to the Sangha and preaches them. Sometimes special events such as festivals are also held.
The day after Asalha Puja is the entrance to the pansa or vassa, the annual three-month rain retreat for Buddhist monks (Thai: Khao Pansa).