Buddha Purnima (full moon day of the lunar month Vaishaaka) is considered the most sacred day in the Buddhist calendar. This day encompasses the birth, enlightenment (Nirvana), and passing (Parinirvana) of Gautama Buddha. At the first conference of the World Fellowship of Buddhist held in Sri Lanka in 1950, it was Nepal to declare a public holiday on Buddha Purnima and request all other countries for the same.
Many devotees visited Boudhanath Stupa on this day. This is the largest stupa in Nepal which was built in 5th century during the reign of King Mānadeva. This stupa is said to entomb the remains of a Kasyapa sage venerable both to Buddhists and Hindus. As of 1979 this is listed as a UNESCO World Heritage Site.