May Day has traditionally been highly significant in many European cultures. The Celtic year was divided into two parts: one began on May 1st, the other on November 1st. In the Welsh tradition these are given the names Calan Mai and Calan Gaeaf, and in the Irish tradition, Beltane (sometimes, Beltaine, Beltine or Beltene) and Samhain. At these points of transition, the boundary between the ordinary world and the Otherworld was thought to be weakened. We see a hint of the possible significance of Beltane in the story of 'Lludd and Llefelys', in which it is said that hearing the screams of the dragons fighting on ‘May eve' might lead to infertility. There is also a reference to May 1st in 'How Culhwch won Olwen', where two men become part of an agreement to fight for a maiden every ‘May day’ until ‘Judgement Day’*.