听力原文： Halloween is celebrated every year. But just how and when did this custom happen? Is it just a harmless celebration? The word 'Halloween' actually has its origins in the Catholic Church. It comes from a change of All Hallows Eve. All Hallows' Day, or All Saint's Day, November 1, is a Catholic day. But in the 5th century BC, summer officially ended on October 31. It was believed that, on that day, the spirits of all those who had died throughout the year would come back in search of living bodies for the next year. It was believed to be their only hope for the after life. Naturally, the living did not want to be taken away. So on the night of October 31, villagers would put out the fires in their homes, to make them cold and unwanted. They would then dress up in all manners of strange customs and noisily walked around the neighborhood, being as wild as possible in order to frighten away spirits looking for living bodies. Some accounts tell of how they would burn someone as sort of a lesson to the spirits. How often is Halloween?