Halloween (or Hallowe'en) is an annual holiday observed on October 31, primarily in the United States, Canada, Ireland, and the United Kingdom. It has roots in the Celtic festival of  Samhain  and the Christian holiday  All Saints' Day , but is today largely a secular celebration. Common Halloween activities include  trick-or-treating , wearing costumes and attending costume parties, carving  jack-o'-lanterns , ghost tours, bonfires,  apple bobbing , visiting haunted