Halloween originated from the ancient Celtic festival of Samhain, celebrated on November 1st. The Celts believed the boundary between the living and the dead became thin on Samhain, allowing spirits to cross over. People wore costumes and carved turnips to ward off spirits. As Christianity spread, the holiday was changed to All Saints' Day on November 1st. Children would go door-to-door begging for food and money, which evolved into modern trick-or-treating. Pumpkins replaced turnips as the popular vegetable for carving jack-o'-lanterns. Today, Halloween is celebrated with costumes, parties, trick-or-treating, and eating candy.