holiday, October 31, now observed largely as a secular celebration. As the eve of All Saints' Day, it is a religious holiday among some Christians.

In the 7th century AD, Pope Boniface IV established All Saints' Day, originally on May 13, and in the following century, perhaps in an effort to supplant the pagan holiday with a Christian observance, it was moved to November 1. The evening before All Saints' Day became a holy, or hallowed, eve and thus Halloween. By the end of the Middle Ages, the secular and the sacred days had merged. The Reformation essentially put an end to the religious holiday among Protestants, although in Britain especially Halloween continued to be celebrated as a secular holiday. Along with other festivities, the celebration of Halloween was largely forbidden among the early American colonists, although in the 1800s there developed festivals that marked the harvest and incorporated elements of Halloween. When large numbers of immigrants, including the Irish, went to the United States beginning in the mid 19th century, they took their Halloween customs with them, and in the 20th century Halloween became one of the principal U.S. holidays, particularly among children.

As a secular holiday, Halloween has come to be associated with a number of activities. One is the practice of pulling usually harmless pranks. Celebrants wear masks and costumes for parties and for trick-or-treating, thought to have derived from the British practice of allowing the poor to beg for food, called “soul cakes.” Trick-or-treaters go from house to house with the threat that they will pull a trick if they do not receive a treat, usually candy. Halloween parties often include games such as bobbing for apples, perhaps derived from the Roman celebration of Pomona. Along with skeletons and black cats, the holiday has incorporated scary beings such as ghosts, witches, and vampires into the celebration. Another symbol is the jack-o'-lantern, a hollowed-out pumpkin, originally a turnip, carved into a demonic face and lit with a candle inside. Since the mid 20th century, the United Nations Children's Fund (UNICEF) has attempted to make the collection of money for its programs a part of Halloween.