The international Buddhist holiday of Vesak is the day commemorating the birth, Enlightenment, and Parinirvana (passing away) of Lord Buddha. According to the Southern Buddhist tradition, these three events all occurred on the full-moon day of the Indian month Vaisakha (April-May). Though the Northern Buddhist tradition assigns the Buddha’s Enlightenment and Parinirvana to different calendar days, the World Fellowship of Buddhists has designated Vesak the major Buddhist holiday. It is a day when Buddhists of all affiliations should express their homage and dedication to the Supreme Teacher whose appearance in this world opened up the gates to the highest happiness and peace.
In the Buddhist tradition, on days of special religious significance, many formally become Buddhist lay disciples. One becomes a Buddhist lay disciple by means of two steps: Going for Refuge to the Three Jewels and undertaking the Five Precepts. Also on special days such as Vesak, lay disciples commonly undertake to observe, for a full day and night, a more stringent set of eight precepts, modeled on the disciplinary code of a novice monk or nun. (Becoming a Buddhist Lay Disciple)