There is no evidence that any group of Celts celebrated all of the eight dates on our list at any one time.
Four of these dates are precisely set by the movements of the heavens, have been honoured for millenna, and were considered important enough to have had vast stone alignments built some 6000 years ago in their honour. The constancy of those shafts of sunlight, year after year, accurately and unfailingly channelled down those ancient sone passages continues to dumbfound generationsas they stand witness to the astronomical and engineering expertise of men (and maybe women) 6000 years dead.
Ireland's Knowth and Newgrange, for example were built around 4000 BC, while the Celts arrived in Ireland and Switzerland between 600-500 BC, suggesting that the Celts continued the practice of marking the big solar dates already in place. Ireland's Knowth Cairn was built to mark the two equinox dates, Newgrange the two solstice dates. These vast stone alignments, precisely engineered to allow the sun's rays through a long passage and flood a chamber with light at the end of it on specific days of the year are as fascinating, awe-inspiring and accurate today as they were six millenia ago.
The remaining four dates evolved socially, connected to growth, to crops and to survival.
All eight celebrated together create a wonderful collection of ancient celebratory dates connecting the earth and the heavens, the past and the present.
For the Celts, the day started at sunset, not at midnight, and carried on until the following sunset. Therefore, special celebratory days commenced at sunset, and this tradition, or fragment remains with us still, in the Christian feasts of Christmas Eve, the day before Christmas, and Hallowe'en, originally Hallow eve, or the day before the feast of All Hallows, in early November which the Celts recognised as the beginning of their yearly cycle.
Imbolc, February 1st
On the islands on the edge of Europe, among the peopls known as the insular Celts, this is the first day of Spring. Strongly associated with the pagan Goddess Brigit, Brigid, or Brigitta who was known throughout Europe, Brigit was so beloved that she made an easy transition to Christianity when the time came. Second only in popularity to St. Patrick, Brigid, who founded her convent in Kildare, is often referred to as the Mary of the Gaels`. In recent years, a flame to her was re-kindled in Kildare, and devotees ensure the candle is constantly alight.
The Spring Equiox, March 21st
The Spring equinox marks the time of year when day and night are of equal length.
Although the Celts did not measure their time in hours and minutes as we do today, they were extremely aware of it, and capable of calculating startlingly accurate astronomical measurements, as were the generations before them.
A good example of how time was masured in Ireland long before the arrival of the Celts is the cairn at Knowth, near Newgrange.
At sunrise on both Spring and Autumn equinox days, the sun enters a 100 foot long passage and lights up a small chamber at the end of it, which contains geometrical drawings. Interestingly, the famous Newgrange solstice passage is shorter, at 66 feet, but both feats of engineering were constructed some 6000 years ago, and are still aacurately measuring the stately passage of time.
The Christian feast of Easter mirrors in many ways the recognition of fertility and rebirth the ancient peoples associated with this time of the year, and is to this day, calculated by the moon as were many of the moveable Celtic and pre-Celtic feasts.
Bealtaine, May 1st
This is the traditional beginning of Summer in the Western islands at the edge of Europe. The date was not strictly celebrated on May 1st, but generally within the fortnight surrounding it, and certainly with a reference to the full moon. Several May 1st customs abound in Europe; Maypole dancing, washing your face in the early dew, protecting your house from evil spirits by placing yellow buttercups on the window ledges and doorways. April 30th is also connected to magic and the spirit world in Europe, but not among the insular Celts.
The Celts divided the year into the bright half and the dark half: Bealtaine marked the beginning of the bright half.
Summer Solstice, June 21st
The Celts, like those before them recognised the movements of the heavens, and recognised the significance of the solstice as the longest/shortest days of the year. Newgrange, in the Boyne Valley, Ireland, gives its name of a complex collection of passage graves and alignments, though not Celtic in origin, have long associations with the Celts and sun worship. Although the main alignment here is for the Winter solstice, a smaller alignment to the summer solstice exists to the north of this larger one, and is not open to the public. The practice of visiting Newgrange at sunrise becomes more popular with every passing year.
June 23rd became St. John's Eve and the night that bonfires were lit in Ireland for centuries and up until today. Traditionally, people and livestock were expected to jump over these fires to protect themselves from evil spirits. Another classic mix of paganism and Christianity on the western edge of Europe.
Lunasa, August 1st
This feast occurs sometime in early August. It is not actually a thanksgiving time, but more a time of appeasement. The crops are not yet in, but almost, and a spell of bad weather could still cause destitution, so the ancient peoples wisely asked their Gods to allow the harvest to happen safely. The Christian thanksgiving is different, celebrating when the job is done.
The Celtic day started at sunset, not at midnight, and carried on until the following sunset. Therefore, special celebratory days commenced at sunset, and this tradition, or fragment remains with us still, in the Christian feasts of Christmas Eve, the day before Christmas, and Hallowe'en, originally Hallow eve, or the day before the feast of All Hallows.
Autumn Equinox, September 21st
As with the Spring equinox, this date marks a time in nature when day and night are equal. From now on, the night or sleep time will visibly increase. Knowth, in Ireland is a 6000 year old example of a precisely engineered 100 ft long passage which allows a shaft of sunlight to penetrate it at sunrise, and light the small chamber at the end of the passage on both equinox dates. Interestingly, this longer passage, though less well known, required event greater engineering skills than the better known, but 40 ft shorter one at Newgrange, which allows the sun to penetrate on the two solstice dates.
The Egyptians built their sphinx to point directly at the equinox sun, also celebrating this sun festival.
Samhain, October 31st
Again, as the chill of Winter approached, the Celtic peoples marked the end of their year around this time. It was a logical and practical end, as the trees were now almost bare, growth suspended and hopefully food in store for the coming times.
Christianity adapted these days into the feast of All Hallows, with the day before it becoming known as Hallowe'en, or the Eve of All Hallows. Like the pagan tradition before it, the Christians also remembered the dead. Pagan lore tells us that on this one night in the year, the souls of the dead can come back to where they once lived, and in many areas of Ireland the houses are still prepared and cleaned for these other- worldly visitors.
Some Celtic peoples divided time using the moon; the bright two weeks from new moon to full moon, followed by the dark two weeks when the moon gets smaller and the nights darker until the blackout, when the new moon appears again. For them, night came first, followed by day. They also divided the year into the light half and the dark half. Samhain marked the beginning of the dark half.
Winter Solstice, December 21st
The Celts, like those before them recognised the movements of the heavens, and in particular recognised the solstice as the shortest day of the year. The great stones at Newgrange, though not Celtic in origin, were set in place so that at sunrise on the 21st-23rd of December, a shaft of sunlight penetrates a 66 ft long covered passage and dramatically illuminates the inside of a stone chamber, lighting as it does, drawings on the stone walls. For those lucky enough to access the chamber, this never fails to thrill, providing of course, that the morning is clear and the sunrise visible. Part of the Boyne Complex, the main alignment at Newgrange pays homage to the Winter solstice, and the incredible builders, astronomers and mathematicians capapble of building such a precise structure over 6000 years ago.
A testimony that the sun will `rise` again, bring heat, warmth, light and growth to the people below, this beautiful festival in the darkest days has connections to the Roman feast of Saturnalia and the Christian Christmas.