Halloween is celebrated on October 31st and involves wearing costumes and participating in traditions. Children go trick-or-treating by going door-to-door asking for treats, and if none are given a trick is played. People also carve jack-o-lanterns and attend costume parties. The celebration originated with the Celts in Britain as a festival to mark the end of the harvest season and onset of winter, believing it was a time when spirits could more easily cross into our world.