Buddha's birthday is the eighth day of the fourth lunar month every year, which is the day when northern Buddhism commemorates and celebrates the birth of Sakyamuni, the founder of Buddhism. Buddha's Birthday Festival, also known as Buddha's Birthday and Buddha's Birthday Festival, is the eighth day of the fourth lunar month every year, which is the birthday of Buddha Sakyamuni. Born in 623 BC, Sakyamuni Buddha was the prince of Kapilowei (present-day Nepal), an ancient Indian kingdom. It is an important ceremony in ancient Indian Buddhism, and its source lies in the historical record of the birth of Sakyamuni. Legend has it that when Sakyamuni was born, he touched the sky and the ground with one finger, and the earth shook and Kowloon spat water to take a bath. Buddhists of all nationalities in the world often commemorate the Buddha's birthday by bathing Buddha.

The eighth day of the fourth lunar month is one of the most solemn Buddhist festivals in a year, and it is the birthday of Sakyamuni Buddha. China was confined to monasteries in the Eastern Han Dynasty, and spread to the people in the Wei, Jin, Southern and Northern Dynasties. There are different records about the time of bathing Buddha in historical books. In Mongolian Tibetan areas, April 15 is the Buddha's birthday, that is, the Buddha's enlightenment day and the Buddha's nirvana day, so a Buddha washing ceremony will be held on this day. Buddhism in the Han nationality area in the Northern Dynasties was held on the eighth day of the fourth lunar month, and then it changed and developed continuously. In the north, it is held on the eighth day of the twelfth lunar month (Laba Festival), while in the south, it is still held on the eighth day of the fourth lunar month, which has been common until today (commonly known as "April 8"). The water-splashing festival of the Dai nationality is held in June of the Dai calendar (April of the summer calendar). In the morning, men, women and children bathe and change clothes, and when they go to the Buddhist temple to worship Buddha, they have the nature of bathing Buddha.