October 31 is the Feast of All Hallows' Eve...Halloween.
Halloween or All Hallows' Eve is not a liturgical feast on the Catholic calendar, but the celebration has deep ties to the Liturgical Year. These three consecutive days — Halloween, All Saints Day and All Souls Day — illustrate the Communion of Saints. The Church Militant (those on earth, striving to get to heaven) pray for the Church Suffering (those souls in Purgatory) especially on All Souls Day and the month of November. We also rejoice and honor the Church Triumphant (the saints, canonized and uncanonized) in heaven. We also ask the Saints to intercede for us, and for the souls in Purgatory.
Since Vatican II, some liturgical observances have been altered, one example being "fast before the feast" is no longer required. Originally, the days preceding great solemnities, like Christmas and All Saints Day, had a penitential nature, requiring abstinence from meat and fasting and prayer. Although not required by the Church, it is a good practice to prepare spiritually before great feast days.
In England, saints or holy people are called "hallowed," hence the name "All Hallow's Day." The evening, or "e'en" before the feast became popularly known as "All Hallows' Eve" or even shorter, "Hallowe'en."
Since the night before All Saints Day, "All Hallows Eve" (now known as Hallowe'en), was the vigil and required fasting, many recipes and traditions have come down for this evening, such as pancakes, boxty bread and boxty pancakes, barmbrack (Irish fruit bread with hidden charms), colcannon (combination of cabbage and boiled potatoes). This was also known as "Nutcrack Night" in England, where the family gathered around the hearth to enjoy cider and nuts and apples.
Halloween is the preparation and combination of the two upcoming feasts. Although the demonic and witchcraft have no place for a Catholic celebration, some macabre can be incorporated into Halloween. It is good to dwell on our impending death (yes, everyone dies at one point), the Poor Souls in Purgatory, and the Sacrament of the Sick. And tied in with this theme is the saints, canonized and non-canonized. What did they do in their lives that they were able to reach heaven? How can we imitate them? How can we, like these saints, prepare our souls for death at any moment?