Halloween's origins can be traced back to the ancient Celtic festival known as Samhain, which was held on November 1 in contemporary calendars. It was believed that on that day, the souls of the dead returned to their homes, so people dressed in costumes and lit bonfires to ward off spirits.

Samhain is a Gaelic festival marking the end of the harvest season and beginning of winter or "darker-half" of the year. It is held on 1 November but with celebrations beginning on the evening of 31 October, since the Celtic day began and ended at sunset.