The exact date of Vesākha varies according to the various lunar calendars used in different traditions.
Vesak is an annual holiday observed traditionally by practicing Buddhists in many Asian countries like Nepal, Hong Kong, Singapore, Vietnam, Thailand, Cambodia, Malaysia, Sri Lanka, Myanmar, Indonesia,Pakistan, India, and Taiwan.
Sometimes informally called “Buddha’s birthday,” it actually encompasses the birth, enlightenment Nirvana, and passing (Parinirvana) of Gautama Buddha.
The Buddha gave an important teaching to the assembled monks on that day 2,500 years ago called the ‘Ovādapātimokha’ which laid down the principles of the Buddhist teachings.
In Thailand, this teaching has been dubbed the ‘Heart of Buddhism’.