Do you ever wonder about the origins of Halloween customs like trick-or-treating? Why do we carve pumpkins? Where did this unusual, magical, spooky holiday come from, anyway?
Years ago when I was a folklore student, I did my research on the origins of Halloween, and I've shared some fun info online on my Lunagirl feature article Between the Worlds: The Origins of Halloween and Its Customs.
Below is an except -- read the full version at http://lunagirl.com/pages/origins-of-halloween

"Among the ancient Celtic peoples of Europe, the end of October was marked by the festival of Samhain. Samhain (sometimes translated hesitantly as "summer's end") was one of four major yearly festivals of the Celtic calendar. As the life of these people was embedded in and dependant upon the cycles of nature, their calendar was based on the movement of the seasons. The festivals can be seen as recognizing and celebrating important transition point in the seasonal year.
The Celts measured time primarily by the moon, and these four festivals may be compared to the lunar stages. Candlemas recognized the waxing (growth) of the year, Beltane the fullness, and Lammas the waning, while Samhain celebrated the new or dark moon, both the end and the beginning of the cycle.
In the Celtic calendar (as many other ancient calendars) a "day" began at sunset the day before, and holiday observations began on the "eve." As a survival of this world view, we celebrate All Hallow's Eve and Christmas Eve! Jewish holidays similarly begin at sunset. Imbolc, later Christianized as Candlemas, celebrated the beginnings of the return of the light and warmth of the sun. It was thought to be the best time for predicting the weather of the coming spring -- a belief that survives today in Groundhog Day. Beltane or May Day signified the beginning of summer, a time of warmth, abundance, and fertility. Lughnasa, later known as Lammas, was the harvest festival in these northern lands, a time of gathering in -- of enjoying the fruits of summer and beginning preparations for the long winter ahead.
Samhain (beginning at sundown on October 31) was the Celtic new year festival, and the most powerful transition of the year. It marked the end of one year and the beginning of another, and the entry of winter. The waning light and warmth of the sun gives way to darkness and cold. The harvest was completed and crops were put away for the winter. As the time of the death of the old year, Samhain was the appropriate time to remember the dead; their spirits were believed to return to earth on this night. Samhain symbolized death -- death which is not final but rather an incubation necessary before rebirth in the spring."