Tomorrow (Friday, June 21, 2013) is the date of the summer solstice within the Northern Hemisphere. In the Southern Hemisphere, by contrast, tomorrow will be the date of the winter solstice.

Solstices have long been observed as important seasonal festivals in many traditional cultures. Accordingly, June 21 being a solstice day, that date 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, tomorrow is Litha (or Midsummer), celebrating the summer solstice. In the Southern Hemisphere, however, it will be Yule (or Midwinter), celebrating the winter 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 June 21, the summer solstice occurs in the Northern Hemisphere, while the winter solstice occurs simultaneously 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 summer solstice, as the tilt of the Earth’s axis slowly shifts, the days grow progressively longer, and the nights increasingly shorter. This slow shift peaks tomorrow, with the advent of the summer solstice itself, which will be the longest day (and the shortest night) of the year. After the summer solstice, the subsequent days will then begin to grow progressively shorter, and the nights increasingly longer — until this pattern also eventually peaks, and then reverses itself once again, with the advent of the winter solstice (the shortest day, and the longest night, of the year).

The summer solstice is technically regarded as being the actual start of summer, the first day of the official summer season. Being the longest day of the year, immediately after the summer solstice the days may begin to gradually grow slightly shorter, but they don’t begin to grow any cooler; weather-wise, at least, summer 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 increasing hours of daylight “max out” before transitioning toward an equally steady decrease (or vice versa). In this particular sense, perhaps solstice festivals might indeed be rightfully regarded as “mid”-summer or “mid”-winter seasonal festivals.

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As I write, Wiccans and other Neopagans in the Northern Hemisphere will tomorrow celebrate their midsummer festival, traditionally known as Litha. Meanwhile, their fellows in the Southern Hemisphere will simultaneously be celebrating the midwinter festival known as Yule.

Litha or Midsummer centers upon 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.

Yule or Midwinter instead observes 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.

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

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