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.

Wales is a country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the east, the Bristol Channel to the south, and the Celtic Sea to the south-west. As of 2021, it had a population of 3.2 million. It has a total area of 21,218 square kilometres (8,192 sq mi) and over 2,700 kilometres (1,680 mi) of coastline. It is largely mountainous with its higher peaks in the north and central areas, including Snowdon, its highest summit. The country lies within the north temperate zone and has a changeable, maritime climate. Its capital and largest city is Cardiff.