Tradition: Buddhism
Link: http://www.hds.harvard.edu/life-at-hds/religious-and-spiritual-life/multifaith-calendar/about-the-multifaith-calendar
The commemoration of Buddha’s birth, enlightenment, and parinirvana, celebrated on the day of the full moon of the sixth lunar month in Southeast Asian cultures; in Tibetan culture, Wesak commemorates only the the enlightenment and parinirvana. The dates of this celebration vary significantly among Buddhist cultures and communities.