The birthday of the historical Buddha or Shakyamuni Buddha, known as Vesak in several countries, celebrates the birth of the child who became Prince Siddhartha around the end of the 4th century B.C. This is a holy occasion for all Buddhists, but is celebrated on different dates depending on the school of Buddhism or country to which one belongs. In several Asian countries, it is observed on the eighth day of the fourth month of the lunisolar calendar, which this year falls on May 15. In several South and Southeast Asian countries, it is celebrated on the first full moon of May, which falls on May 23.