Sabbats.
The eight Sabbats of the "Wheel of the Year" constitute the major holidays celebrated by members of the various Pagan religions (by far the largest of which is the Gardnerian-style Witches) that have grown up in the United States since the mid-1960s. These are usually supplemented by a few of the most important holidays peculiar to the (usually) ancient Pagan religion that a local coven or family of covens (or groves, etc.) is most partial to; the most popular ancient religious traditions are the Celtic, Greek, Mesopotamian, Egyptian, and Nordic, in roughly that order.
The eight Sabbats fall into two subgroups: the Greater Sabbats, comprising the Celtic cross-quarter days; and the Lesser Sabbats, comprising the English quarter days, that is, the solstices and equinoxes. The most common names used by Witches for the Greater Sabbats are Brigid (on February 1), Beltane (on May 1), Lughnasad (on August 1), and Samhain (pronounced "sa-oo-en," on November 1), and those for the Lesser Sabbats are Eostar (spring equinox, about March 22), Litha (summer solstice, about June 22), Mabon (fall equinox, about September 22), and Yule (winter solstice, about December 22).
In a Gardnerian-type coven, which meets for an esbat at each full moon during the year, each Sabbat is observed by means of a special ritual that is inserted into the middle of the coven's ordinary working ritual (something like the "proper" of the Catholic Mass). Hence there is a set of eight such special rituals in a coven's "Book of Shadows" (in effect, its liturgical manual); the other four or five esbats during the year use the basic ritual.
Almost every religious body in the world (except for the Muslims, whose calendar totally ignores the solar year) has at least one major holiday that falls on or fairly near a solstice or equinox. After all, the changes in the Sun during the course of each year are fairly dramatic in most climes, and are therefore dealt with somehow by the myths and rituals of most cultures. Stonehenge proves that formal marking of the solstices goes back about 5,000 years in Britain. It is in this sense that the modern Witches claim that their Sabbats are the "original" or "oldest" holidays known to mankind.
The research of Gerald Hawkins, confirmed by the astronomer Fred Hoyle, has demonstrated that the lines of sight at Stonehenge (and other British megalithic monuments) point at the rising and setting positions of the sun on the days of the solstices and equinoxes, and of the moon when it reaches its maximum northern or southern position during each 18.67-year cycle. Furthermore, the correction of radiocarbon dating by Colin Renfrew demonstrated that these lines of sight at Stonehenge are the basis for the oldest parts of the monument, built around 3000 B.C.E. (building on it continued for about 1500 years). What this means is that around 3000 B.C.E., before the first pyramids were built in Egypt, the people living in England had built a stone computer that enabled them to predict the regular events of the solar year (the solstices and equinoxes), and also enabled them to predict all solar and lunar eclipses. If the people in Britain, like the people in Mesopotamia (with whom they traded), believed that the Sun, Moon, and planets were the "visible gods," then this ability to predict eclipses must have given them a great sense of being in control, and must have conferred great prestige and power on the specific people who were in charge of operating Stonehenge--for, like an abacus, it did have to be operated. There were stone counters that had to be moved from one hole to the next at the exact intervals needed to keep track of the motions of Sun and Moon. Hence we can be sure that the solstice and equinox solar festivals are the oldest ones celebrated in the British Isles.
The popular attribution of Stonehenge to "Druids" is therefore historically impossible, for the Druids were specifically the priestly caste of the Celtic peoples, who did not arrive in Ireland until about 500 B.C.E., give or take a few centuries. (Dating early British history is very difficult, but the Celts were certainly much too late--by at least 2000 years--to have built Stonehenge.) Furthermore, the Celts brought with them a very different set of holidays, based apparently on the weather pattern of northern Europe, rather than directly on the Sun.
The English called the solstices and equinoxes, on about March 22, June 22, September 22, and December 22, the quarter days, because on them the quarterly rent payments were due during the Middle Ages. The Celtic festivals, on the first day of February, May, August, and November, are called the cross-quarter days, because they fall in between the quarter days. Almost all of these days have several different names, reflecting their long and complex history, which we will discuss later.
The brothers Aylwin and Brinsley Rees point out, in their authoritative Celtic Heritage, that in the Celtic myths everything, all time and space, is conceived as divided and subdivided into joined but opposing halves, and that danger is associated with the seams between such halves. Thus the Celtic year began on Nov. 1, at Samhain, the festival that marks the end of good weather. (The Greeks also divided their year into two such halves, the good-weather half beginning when it was safe for Apollo's sacred ship to sail between Delos and Athens, about May, and ending when the storms of Maimakterion, about November, once again made shipping unsafe; these dates were fixed, not by their lunisolar calendar, but by the heliacal rising and setting of the Pleiades each year.) At the seams between the two halves of the year, but especially at Samhain, when the bad half was beginning, the Celts believed that ghosts, fairies--all the inhabitants of the "unseen world" that was the necessary other half of the universe--could slip through into this world; this is one reason why, in areas heavily populated by people of Celtic background, ghosts and witches are still thought to be most active at Hallowe'en and May Day. Likewise, the Celts thought that twilight and dawn, the seams between night and day, are dangerous times; it was especially at twilight that the fairies most likely could carry someone off. Just as the two halves of the year were also divided in half, by Candlemas and Lammas, the night and the day were also divided in half, by midnight and noon, the former in each case again being the more dangerous. In the Celtic calendar, as in almost all ancient calendars, a day began at sunset, which is why Hallowe'en (worn down from All Hallows' Evening) is celebrated the night before November 1.
The two sets of holidays have often been used to symbolize the political struggles of the people living in Britain. The social pattern in Britain has been created by a series of conquests that are historically much easier to disentangle than conquests elsewhere usually have been, largely because Britain's insular isolation has made successful invasions and conquests rather rare. The archaeological evidence reveals migrations of people into the British Isles ever since the end of the last Ice Age, and as long as the islands were sparsely settled, these migrations were apparently peaceful. It has usually been thought that the first military conquest of Britain was carried out by Indo-European-speaking peoples, who were expanding all over Europe between about 2000 and 1500 B.C.E., that these conquerors set themselves up as a ruling class in England, and that they built the last stage at Stonehenge (the massive trilithons) as a cathedral or monument to themselves. Grave doubt has now been cast on all such theories. Colin Renfrew's recent article in Scientific American argued that Indo-European was probably the language of the people who expanded out from Anatolia around 6000 B.C.E., and spread across Europe, building megalithic monuments as they went; hence there probably was no Indo-European conquest, and hence no confrontation between hypothetical matriarchal and patriarchal cultures.
However, there is no doubt about the historical conquest of Britain by Celts in the first millennium B.C.E. It is quite clear that the Celts did set themselves up as a ruling class, and that their priests, the Druids, were a very privileged class, indeed, who exploited the subjugated peasants unmercifully. This seems to be why the common people happily cooperated with the Romans in overthrowing and extirpating the Druids, once the Romans began occupying the island after 50 B.C.E. Since the Druids had emphasized the Celtic cross-quarter days, the people instead took up the Roman festivals, which emphasized the quarter days.
One reason why Christianity began growing rapidly in the Roman Empire in the third century C.E. was that by then the Pax Romana, the "Roman Peace," had broken down; the Western Empire was once again decimated by civil wars, and defenseless against barbarian invasions. In this turmoil, the scholars of the ancient universities--mainly pagans, but with a healthy sprinkling of orthodox and heretical Christians--fled to whatever refuge they could find; and some of them found Ireland, which had never been conquered by the Romans, and which therefore maintained an unbroken Celtic culture. (As a result, while most of Europe was going through the "Dark Ages," Ireland enjoyed a Golden Age until the Viking raids of the ninth and tenth centuries burned the libraries, and the Norman conquest of the twelfth century ended Irish independence.)
When the last Roman legions were called home about 400 C.E., Germanic-speaking peoples began overrunning the now Romano-Celtic island of Britain, and apparently brought with them another version of the northern European weather festivals. The Romano-Celtic peoples, pushed into the remoter areas of their territory (Ireland, Wales, Cornwall, Brittany, and perhaps the Scottish highlands), seem at first to have continued celebrating the Roman festivals as a statement of their cultural identity. However, as Christianity during the next few centuries began spreading into the British Isles, bringing its own version of the solar festivals, and as the Anglo-Saxon ruling classes used Christian doctrines and customs as a way to justify their rule, the Celts gradually tended to revive the cross-quarter days.
Irish Christians began proselytizing England in the second half of the sixth century. The Roman Church sent up its representative, St. Augustine of Canterbury, at the end of the sixth century. The two hierarchies competed enthusiastically. Finally, at the Synod of Whitby in 664 C.E., the Saxon King Oswiu decided to recognize the Roman Church as the official religion of his kingdom, whereupon St. Colman, St. Aidan's successor as Abbot of the Holy Island of Lindisfarne, who had led the argument for the Celtic side, packed up his followers and they "returned to their own land," according to the Anglo-Saxon Chronicles for that year.
Of all the theological differences between the two churches, the one they picked to argue about was how to calculate the date of Easter. The rule established by the Council of Nicaea had not settled the whole issue, since the phases of the moon still had to be determined by a regular calendrical cycle, rather then by direct observation. The Roman Church had, by the seventh century, adopted a 532-year cycle, the "Victorian" cycle (consisting of 28 19-year cycles), to regulate the calendar. But the Celtic Church persisted in using an eight-year cycle, the "Roman" cycle, and also used a different rule for deciding which night was the full moon. The Celtic Easter thus usually fell on a very different date from the Roman Easter.
The story of the Synod of Whitby is recorded in Bede's History of the English Church and People. The Celtic Christians may have wanted to use their own system for calculating the date of Easter in order to make it coincide with the spring festival common among the pagan peoples of Northern Europe, and there is some evidence to support this suggestion in Bede's discussion of the Saxon calendar, which had 12 lunar months, with a 13th month added once every three years. (This calendar might be as much Celtic as Saxon, since it bears some resemblance to the Celtic Coligny calendar, but exploring this is not possible here.)
Let us consider the names of the Saxon months given by Bede, as listed in the following table. The 13th month was inserted between Forelitha and Afterlitha, and a year with 13 months was called a "Threelitha"; so we can deduce that the 13th month was called Litha. Judging by the parallel with the months of Foreyule and Afteryule, Litha must also have been the name of the summer-solstice festival, as Yule was the name of the winter-solstice one.
Likewise, we can guess that if the fall equinox fell in the month after "Weed month," that month was called "Holy month" and the following one was called "Winterfull," that is, the full moon that begins winter. If the fall equinox did not occur in the month after "Weed month," then that month was called "Harvest month," the following month, in which the fall equinox did occur, was called "Holy month," and the "winterfull" moon would have been the next one. This designation of "Holy month" for the month containing the fall equinox was clearly of pagan origin, for there was no church festival of any importance near the fall equinox in the seventh century.

The Saxon calendar.

Name of month Alternative Corresponded
name approximately to
Afteryule Wolfmonth January
Sproutkale Solmonth February
Hlydamonth March
Eosturmonth April
Threemilks May
Forelitha Shearmonth June
Afterlitha Meadmonth July
Weedmonth August
Harvestmonth Holymonth September
Winterfull Holymonth October
Bloodmonth November
Foreyule December
("Solmonth" may have "cake month" rather than "sun month," and what "Hlyda" means is unknown.)
Bede says that the two months called Hlyda (or Hretha, or perhaps Hlytha?) and Eostur were named after goddesses. Not much is known about the Goddess Eostur, but it is from her name that English-speaking peoples derive their name "Easter" for the Feast of the Resurrection, which everywhere else is called "Pasch" or something similar derived from the Hebrew word for Passover. From her we also derive the Easter Rabbit, for the rabbit was one of her sacred animals. Furthermore, this rabbit lays Easter eggs, because in some of the Mystery religions of the Roman period, an egg dyed scarlet was the symbol of the immortality (by means of reincarnation) promised to the initiate. Here we can see the results of Gregory's advice to Augustine, not to destroy the pagan religions in Britain, but to adapt as much of them as possible, giving it all a new, Christian interpretation.
With the invasion in 1066 by the only-recently (and not very deeply) Christianized Normans (who were essentially French-speaking Norsemen), the Celtic peoples in the British Isles very often helped overthrow the local Anglo-Saxon nobility; as a result, the Normans were very receptive to Celtic culture, which is why the Arthurian legends burst forth from Britain at this time, and spread rapidly across Europe. With major Christian festivals tied to the quarter days_Christmas to the winter solstice, Easter and the Annunciation (or Lady Day) to the spring equinox, St. John's Eve and Whitsuntide to the summer solstice, Michaelmas to the fall equinox_any sort of popular opposition to the Christian establishment would naturally tend to seize on the cross-quarter days as occasions for protest, rebellion, and celebration of whatever the established religion was currently opposed to. This is another reason why May Eve and Hallowe'en are associated with "witches"; but, in fact, both the quarter days and the cross-quarter days are equally "pagan" in origin.
But over this wheel of originally pagan agricultural and weather festivals is laid the pattern of Christian movable feasts that depend on Easter, and some folk customs that apparently were once attached to one or the other of the four-holiday systems became attached, in the course of time, to a movable feast. That is, whatever might originally have characterized one set of holidays or the other can hardly be sorted out now. In addition, with a third of the Christian liturgical year, from early February through late June, tied to the movable feast of Easter, customs associated with the holidays during these months have been thoroughly stirred together.
All of these holidays, quarter and cross-quarter days alike, have been adopted by the contemporary Pagan movement. Under Murray's influence, the New Forest coven had originally celebrated only the Celtic cross-quarter days as its Sabbats. Celebration of the quarter days became more common under Valiente's leadership, and by the late 1950s the present system, of celebrating all eight sabbats, had evolved. "Robert," who was initiated into Gardner's original coven in 1957 and is still active in it, says that the original four Sabbats (held on the full moon nearest the traditional date) were potluck feasts for the coven, and the other eight or nine esbats during the year were simple working meetings. In the late 1950s the coven decided to celebrate all eight Sabbats in order to have twice as many feasts during the year--and this is as far back as the concept of the eight-spoked "Wheel of the Year" can be traced.
In the late 1960s, when the Craft movement had spread across America, semi-public Sabbats began to be held. (The first group to hold Sabbats open to non-members was apparently the New, Reformed, Orthodox Order of the Golden Dawn, still perhaps the largest Witchcraft organization in California; their first "open Sabbat" was held in 1968.)
Since 1970, and especially since 1980, it has become common in the United States for the Sabbats to be celebrated outdoors--in public parks, in campgrounds, in rented resorts--by local associ-ations of covens or at national festivals. Whereas the local gatherings may attract a few dozen to a few hundred people, there is now an annual cycle of festivals--approximately one for each Sabbat in each major region of the United States (e.g., New England, southern California, the upper Midwest, or the Southeast) -- regularly attended by thousands of Witches and Pagans. The "Wheel of the Year" of the eight Sabbats, being referred to a mythology about the Goddess and Her Consort, has begun providing a new artistic form, the "Sabbat Ritual," combining drama, poetry, music, costume, and dance, that is becoming equivalent in artistic importance to the Catholic Mass. The "working" (the term "performance" is avoided) of a newly written Sabbat Ritual is usually the climax of a festival. There are already several annual productions that are full-scale oratorios, and some of these are even heading toward the complexity of classical opera. For example, the New, Reformed, Orthodox Order of the Golden Dawn has held a ritual recreating (or at least commemorating) the Eleusinian Mysteries at their fall-equinox Sabbat annually since 1969; the Aquarian Tabernacle in Seattle does much the same at its spring festival; and the rituals of Inanna and Dumuzi, or of Ishtar and Tammuz, have been reconstructed (with great artistic imagination) from the Mesopotamian tablets and reenacted by the Center of the Divine Ishtar in Palo Alto, California, annually since about 1976. The full annual cycle of eight Sabbats provides an even larger form, which will eventually be filled by a set of rituals comparable in some ways to Wagner's Ring cycle.
Because the concept of reviving ancient Pagan religions became popular among the late Romantics, essentially the same set of eight festivals was also devised by Rudolf Steiner's Anthroposophical League (or its philosophical predecessors). As a result, these festivals are also observed by followers of Steiner in the United States, and are built into the annual schedule of the Waldorf Schools, the alternative educational system founded by Steiner in New York, which continues to set the standard for humane, humanistic education through high school throughout much of the Western world.