Wiccan Wheel of the Year ~ The Sabbats
For followers of nature-based spiritual paths, such as the Druidry or Wicca, the dynamics of the changing seasons and the interplay between darkness and light are fundamental. This enduring cycle is an expression of deeper truths, and by making a conscious choice to be active participants in the natural ebb and flow of the year, pagans can find harmony with things on all levels, from the natural to the personal to the divine.
From antiquity, people have celebrated the ever-turning wheel of the year in eight festivals that mark important points in the cycle: the two solstices and the two equinoxes, and four cross-quarter days dividing the time between them. These festivals are common across many pagan traditions, including the Druidic, Wiccan, Celtic and Norse (Asatru) paths.
http://herbalmusings.com/wiccan-wheel-of-year.htm