Halloween is an annual holiday, celebrated each year on October 31, that has roots in age-old European traditions. It originated with the ancient Celtic festival of Samhain, when people would light bonfires and wear costumes to ward off ghosts. In the eighth century, Pope Gregory III designated November 1 as a time to honor all saints; soon, All Saints Day incorporated some of the traditions of Samhain. The evening before was known as All Hallows Eve, and later Halloween. Over time, Halloween evolved into a day of activities like trick-or-treating and carving jack-o-lanterns. Around the world, as days grow shorter and nights get colder, people continue to usher in the season with gatherings, costumes and sweet treats.

Halloween’s origins date back to the ancient Celtic festival of Samhain (pronounced sow-in). The Celts, who lived 2,000 years ago in the area that is now Ireland, the United Kingdom and northern France, celebrated their new year on November 1.

This day marked the end of summer and the harvest and the beginning of the dark, cold winter, a time of year that was often associated with human death. Celts believed that on the night before the new year, the boundary between the worlds of the living and the dead became blurred. On the night of October 31 they celebrated Samhain, when it was believed that the ghosts of the dead returned to earth.

In addition to causing trouble and damaging crops, Celts thought that the presence of the otherworldly spirits made it easier for the Druids, or Celtic priests, to make predictions about the future. For a people entirely dependent on the volatile natural world, these prophecies were an important source of comfort and direction during the long, dark winter.

To commemorate the event, Druids built huge sacred bonfires, where the people gathered to burn crops and animals as sacrifices to the Celtic deities. During the celebration, the Celts wore costumes, typically consisting of animal heads and skins, and attempted to tell each other’s fortunes.

When the celebration was over, they re-lit their hearth fires, which they had extinguished earlier that evening, from the sacred bonfire to help protect them during the coming winter.

By 43 A.D., the Roman Empire had conquered the majority of Celtic territory. In the course of the four hundred years that they ruled the Celtic lands, two festivals of Roman origin were combined with the traditional Celtic celebration of Samhain.

The first was Feralia, a day in late October when the Romans traditionally commemorated the passing of the dead. The second was a day to honor Pomona, the Roman goddess of fruit and trees. The symbol of Pomona is the apple, and the incorporation of this celebration into Samhain probably explains the tradition of “bobbing” for apples that is practiced today on Halloween.

On May 13, 609 A.D., Pope Boniface IV dedicated the Pantheon in Rome in honor of all Christian martyrs, and the Catholic feast of All Martyrs Day was established in the Western church. Pope Gregory III later expanded the festival to include all saints as well as all martyrs, and moved the observance from May 13 to November 1.