Halloween is celebrated on October 31st in most countries around the world. It is thought to have originated in ancient Celtic and Roman traditions and was known as Samhain (pronounced sow-in). During this time, the people would celebrate by wearing costumes and going door-to-door asking for food. The tradition of trick-or-treating began about 100 years ago in England. Children would go from house to house collecting candy with a bag called a "treasure hunt."