Wesak is the full moon in Taurus every year, despite some other dates that are used in May by various countries. This year, it is May 8th.
The Buddha, Gautama, was born in a Hindu family. He came to teach a better way, at a time when the priests had become very corrupt. So the basis of his teachings is Hindu. The Buddha’s teaching spread through out India and the northern area which includes Tibet, as well as to the east through China and Japan and south to Sri Lanka.
The earlier religion of Tibet was Bon Po. After some time, the Bon Po priests drove out Buddhism. A later ruler of Tibet, believing that Buddhists were more peaceful and easier to govern, sent to India for someone to come and teach the people Buddhism. No teacher was willing to come, but finally Atisha, one of the disciples of the Great Tantric Master Agastya volunteered. The Buddhism he taught was influenced by his tantric mastery, which includes worship of the Divine Feminine. As that is expressed in Tibetan Buddhism, She is Tara, rather than several named Devis. Tara is worshiped as White Tara, Green Tara and more, as ways to approach the Divine Feminine.
The Tara revered in Hindusim is different from the Hindu versions. Hindu Tara is She Who Takes Us Over the Ocean of Samsaras (accumulation of karma from all previous and the present life.)