Vesak/Visakha Puja (Buddha Day)

[Vesak is the] most important of the Theravada Buddhist festivals, commemorating the birth, enlightenment, and death of the Buddha. The event is observed on the full-moon day of the lunar month Vesakha, which falls in April or May. The day is observed as a public holiday in many Southeast Asian countries. It is marked by special devotional services and various deeds intended to be meritorious, such as the presentation of food or alms to monks or the release of captive birds.

Encyclopaedia Britannica