Today (Friday, December 21, 2012) is the date of the winter solstice within the Northern Hemisphere. In the Southern Hemisphere, by contrast, today is the date of the summer solstice.

Solstices have long been observed as important seasonal festivals in many traditional cultures. Accordingly, Dec 21 being a solstice day, today is also a significant holiday on the religious calendars of Wiccans and other contemporary Pagans.

However, which particular Wiccan or Neopagan holiday it happens to be will vary, depending upon which particular hemisphere of the world one happens to reside in.

In the Northern Hemisphere, it is Yule (or Midwinter), celebrating the winter solstice. In the Southern Hemisphere, however, it is Litha (or Midsummer), celebrating the summer solstice.

Since the season prevailing in one hemisphere is always the opposite of the season prevailing in the other hemisphere, seasonal holidays between the two hemispheres are staggered, or out of sync from each other, by some six months.

So, on December 21, the winter solstice occurs in the Northern Hemisphere, while the summer solstice occurs in the Southern Hemisphere.

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Solstices have to do with the seasonal shifts in the tilt of the Earth’s rotational axis relative to the Sun, the angle of which is responsible for our planet experiencing seasons at all. A hemisphere currently tilted toward the Sun receives more direct sunlight, and so experiences the warmth of summer; the other hemisphere, simultaneously tilted away from the Sun, receives less direct sunlight, and so experiences the coldness of winter.

Up until the winter solstice, the days grow progressively shorter, and the nights increasingly longer. This pattern peaks with the advent of the winter solstice itself, which is the shortest day (and the longest night) of the year. After the solstice, the subsequent days will then begin to grow progressively longer, and the nights increasingly shorter — until this too peaks and reverses itself once again, with the eventual advent of the summer solstice (the longest day, and the shortest night, of the year).

The winter solstice is technically regarded as being the actual start of winter, the first day of the official winter season. Immediately after the winter solstice, the days may begin to grow longer, but they don’t begin to grow warmer; weatherwise, winter has really only just begun.

On the other hand, solstices also mark the midpoints of those long seasonal cycles during which the strength and presence of the sun in the sky is either at its greatest or at its weakest. A solstice marks the point at which long periods of steadily decreasing hours of daylight “max out” before transitioning toward an equally steady increase (or vice versa). In this sense, perhaps, solstice festivals might be regarded as “mid”-winter or “mid”-summer seasonal festivals.

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As I write, Wiccans and other Neopagans in the Northern Hemisphere are today celebrating the midwinter festival known as Yule. Meanwhile, their fellows in the Southern Hemisphere are simultaneously celebrating the midsummer festival known as Litha.

Yule or Midwinter centers upon the winter solstice, the shortest day of the year, and the transition of the Sun from a decreasing to an increasing presence in the sky. It marks the beginning of the annual period in which light, warmth, and brightness (and everything that those characteristics may suggest, or symbolically signify) are once again in their ascendancy.

As a kind of “solar rebirth,” Yule or Midwinter also represents an annual transitional period or turning point toward overall rebirth and renewal — of the sun, of associated sun or solar gods, of new light, of new life, of fertility of whatever sort, of new beginnings generally.

Litha or Midsummer instead observes the summer solstice, the longest day of the year, and the peak of the Sun’s light, warmth, and brilliance. In contrast with Yule or Midwinter, Litha or Midsummer also marks the inevitable transition of the Sun into its “annual retreat,” beginning a cycle involving an increasingly diminishing solar strength and presence in the sky.

So, to my Wiccan friends and readers in the Northern Hemisphere, may I today wish you all “Blessed Yule!”

And to my Wiccan friends and readers in the Southern Hemisphere, may I in turn wish you all “Blessed Litha!”