Vesak (from the name of the second month in the Hindu calendar) is the most holy time in the Buddhist calendar. Vesak is also known as Visakah Puja or Buddha Purnima in India, Visakha Bucha in Thailand, and Wesak in Sri Lanka.

It commemorates the birth, Enlightenment and passing of Gautama Buddha on the one historical day, the first full moon day in May, except in a leap year when the festival is held in June.

It is celebrated throughout Southeast Asia where Theravada Buddhism is prevalent. In Thailand, Buddhists celebrate Vesak with mass releases of caged birds, sacred chants, fasting and other religious observances. At the Sakya Muni Buddha Gaya Temple in Singapore, devotees donate money to the temple and in exchange are allowed to place gold leaf onto a small statue of Buddha. As the day wears on, the Buddha is almost entirely covered in a fresh layer of gold leaf.

A similar holiday, called Hanamatsuri or "Flower Festival", is celebrated in Japan on April 8. However, Hanamatsuri commemorates only the Buddha's birth.