Halloween is a holiday celebrated each year on October 31, and Halloween 2021 will occur on Sunday, October 31. The tradition 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, carving jack-o-lanterns, festive gatherings, donning costumes and eating treats.
By 43 A.D., the Roman Empire had conquered the majority of Celtic territory. In the course of the 400 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.