The Gaelic for the May Day festival is Beltane. Usually it is held on 1 May, or about halfway between the spring equinox and the summer solstice. It was widely observed historically, throughout Ireland, Scotland and the Isle of Man. It is one of the four Gaelic seasonal festivals—In Irish the name for the festival day is Lá Bealtaine, in Scottish Gaelic Là Bealltainn and in Manx Gaelic Laa Boaltinn/Boaldyn. Other seasonal festivals are Samhain, Imbolc and Lughnasadh—and is similar to the Welsh Calan Mai.
Beltane is associated with important events in Irish mythology and is mentioned in some of the earliest Irish literature. It marked the beginning of summer and was when cattle were driven out to the summer pastures. Also known as Cétshamhain (“first of summer”), rituals were performed to protect the cattle, crops and people, and to encourage growth. Bonfires were kindled and especially for the occasion, and their flames, smoke and ashes were deemed to have protective powers. Household fires would be extinguished and then they would relight them from the Beltane bonfire. The get-togethers would be accompanied by a feast, and some of the food and drink would be offered to the Aos Sí (fairies or elves). Leaping over the flames or embers would take place and the people with their cattle would walk around or between bonfires. Their home doors, windows and livestock would be decorated with yellow May flowers, it was thought they evoked fire. In parts of Ireland, people would make a May Bush: typically a thorn bush or branch decorated with flowers, ribbons, bright shells and rushlights. Holy wells were also visited, while Beltane morning and night dew was thought to bring beauty and maintain youthfulness. Many of these customs were part of May Day or Midsummer festivals in other parts of Great Britain and Europe.
Beltane celebrations had largely died out by the mid-20th century, although some of its customs continued and in some places it has been revived as a cultural event. Since the late 20th century, Celtic neopagans and Wiccans have observed Beltane, or something based on it, as a religious holiday. Neopagans in the Southern Hemisphere often celebrate Beltane at the other end of the year (around 1 November).