The Old Ways: Hallows
Samhain (pronounced Sow-wen), also called Hallowmas, is the final festival in the Witches' year. It is celebrated on October 31st. The word Samhain means 'Summer's End'. It is the first day of Winter and the Witch's New Year. In earlier agricultural societies, Samhain was also the end of the Harvest, the time to put aside the seed corn for the coming Spring. It was a time for feasting, too, as the weaker animals were culled and killed. Only the livestock most likely to make it through the hard Winters were spared. Feasts consisted of any parts of the animal that couldn't be salted and preserved. It was also considered by the Celts to be one of the Spirit Nights. It was a time to remember the ancestors and tell stories about them. At this time, when the Veils are thin, we honor our ancestors and invite them to attend our celebrations.
Although the modern calendar counts four cross-quarter seasonal celebrations, some early Celts recognized only two: Gamain (Winter's End), on May 1st, and Samhain (Summer's End), on November 1st. As Gamain (or Beltane) is marked by the rising of the Pleiades, so Samhain is marked by it's setting. Many of the old Festivals were timed according to the movement of the stars, a calendar available to everyone, even to the illiterate peasantry.
http://www.cyberwitch.com/Wychwood/Temple/hallows.htm