Beltaine is the start of the light or samos half of the year. It starts now at dusk on the 30th of April and continues through May 1st. For the ancient Celts though, this was a holiday that depended on nature for it's beginning. Traditionally, it was celebrated when the Hawthorn trees began to bloom. This time would vary over the land and was not fixed to the calendar until fairly modern times.
Spelled variously, Beltaine, Belltaine, Beltain, Beltine, Beltane, Bealtaine, Bealteine, Boaldyn (Manx) or Bealtuinn (Scots Gaelic), it is also called May Eve or May Day. This festival was known by various other names in other Celtic countries: Cetshamain (from the Old Celtic - Kentu-saminos, 'first of summer') in Ireland, Shenn do Boaldyn on the Isle of Mann, Calan Mai, Dydd Calen Mai or Cyntefrm in Wales, Calá Mé in Cornwall and Kala-Hañv in Brittany. . It isn't specifically mentioned in the Coligny Calendar, but there are references from the ninth century Irish commentator Cormac, talking about Belo-teniá, 'bon fire of Belos (the bright)'.
-Taken from The Wheel of the Year at Muin Mound Grove, ADF by Rev. Skip Ellison