May Day (beginning of Summer) observances in the Northern hemisphere (see April 30): Calan Mai (Wales)

Calan Mai or Calan Haf, also historically called Cyntefin, is the Welsh celebration of May Day. It marks the beginning of summer and traditionally it involved festivities around bonfires, maypoles, and carol singing. Some of its traditions parallel the Gaelic May Day festival Beltane, and other May Day and Walpurgis Night traditions in Europe.