Halloween has its origins in the ancient Celtic festival of Samhain, celebrated at the end of summer. Samhain marked the Celtic New Year and was believed to be a time when spirits could roam. Irish immigrants brought versions of Halloween traditions to North America during the Great Irish Famine. Originally, the tradition of trick-or-treating involved spirits going from house to house asking for treats to avoid being cursed, and people would carve pumpkins to ward off spirits. Halloween is now celebrated internationally on October 31st and involves costumes, trick-or-treating, and pumpkin carving.