The Celtic New Year is celebrated on November 1st, which is the Celtic feast of Samhain. The word Samhain in Gaelic means "summer's end", and is the most important festival of the Celts. The Celts have always celebrated the opposite forces of existence like darkness and light, summer and winter, night and day, death and life. The Celtic New Year begins with An Geamhradh, the beginning of the dark Celtic winter and ends with Am Foghar, the Celtic harvest. Samhain celebrations are held to mark the beginning of An Geamhradh and the Celtic New Year.

Samhain and the Celtic New Year begin on the evening of October 31st. Oidhche Shamhna or the Eve of Samhain is in fact the most important part of Samhain. Villagers collected the best of their fall harvest and slaughtered cattle for a feast. The heart of each village's celebration was a big bonfire. Villagers put the bones of the slaughtered cattle into this fire. The word 'bonfire' comes from Celtic 'bone fires". The villagers put out all other fires in their homes and lit their hearth fire from the village bonfire, thus binding all the families of the village into one unit.

The eve of the New Year or Oidhche Shamhna was a gap in time. Thus, the spirits from the Otherworld could enter into our world. Rituals on Oidhche Shamhna include providing hospitality to the dead ancestors. They welcomed the dead with food and drink and left the windows and doors of their homes open for the dead to enter. But all spirits from the Otherworld were not good; there were evil spirits too. To keep evil spirits away from their home, they carved images of spirit-guardians onto turnips and placed them at the doors of their homes. As part of the festivities young people wore strange costumes and moved around the village, pretending to be dead spirits visiting from the Otherworld. The Celts believed that on the eve of New Year not only did the boundary between this world and the Otherworld dissolve, but the structure of society dissolved too. Boys and girls would dress up as members of the opposite sex and play pranks on the elders.

Christianity found that a number of Celtic customs were compatible with their religion and hence adopted them. The Church adopted Samhain as the Feast of All Saints or Hallow Tide and Oidhche Shamhna became HallowE'en.