Halloween in American Culture
When Christianity emerged as a global religion, the Church looked for ways to replace the religions of other cultures. A frequent target was the replacement of Pagan and Jewish customs. Ways were sought to keep the other religion's holidays going, but the missionaries had to find a way to imbue them with a Christian twist. Thus a celebration of Christ's birthday was moved to December 25th, in an attempt to usurp the Pagan winter Yule festival held on the 21st. Easter was moved to coincide with the Jewish feast of Passover in the Spring.
The above paragraph may be startling to the average American. Aren't our holidays our own? Aren't they linked to the dates on which the events they celebrate were supposed to have happened? Well, not exactly. We move holidays around on the calendar all the time, such as when we push a day like Labor day or President's day off to the side of the week to create a three-day weekend. The older a holiday custom is, the more likely it is to be moved to a more convenient time and interpreted to the modern culture that observes it.
Halloween started out as Samhain, a Celtic pagan ritual to mark the end of summer, the beginning of harvest season, and a remembrance of the dead. It was still, indeed, their "night before" All Hallowed's Day (a celebration of all Saints), but in time Western culture has abandoned the day of the Saint's entirely and kept the eve before. The separate celebration of a "Day for the Dead" is still done in many parts of the world, most notably in Hispanic culture with "Diaz de los Muertos", which has a lot of skull decorations and dancing in graveyards and such.
Back to Halloween, the idea of having the eve of the Saints be celebrated is one of duality. As observation of the day of the "good", the day of the Saints, an evening before is set aside as the night when the evil spirits frolic about in the world unchecked, before they are banished by the next morning's arrival of light, signifying a new dawn for the world.
This custom of celebrating an "anti-holiday" on the evening before the holiday proper has roots deeper than you might think. Few in Western culture have heard of Krampus, for instance. Krampus is the opposite of Santa Claus, and in parts of Europe, Christmas Eve is not only about hanging stockings and waiting for presents, but fending off a startling devil figure named Krampus, who goes around heckling people, scaring and switching children, and generally running amok. Krampus is yet another Pagan leftover, as one might expect. This is too much excitement for Western culture, and so Santa's schedule got moved to the graveyard shift on the night before Christmas to compensate.
Western culture sometimes seems at a loss to explain Halloween, the anti-holiday that has lost track of it's companion holiday proper. But we seem to have preserved it, mostly because it's fun. The main objections to keeping it around have been from the Christian sects, but the holiday has persevered none the less. Except for April Fool's Day, Halloween with it's costume ritual and tricks is the one holiday whose whole point, when you come down to it, is to not take ourselves so seriously.