The 4 main Subbats were not created by man. They were believed to be here at the beginning of Earth. There was the Summer Solstice , the Winter Solstice , the Vernal Equanox , and Autumnal Equanox .
Summer Solstice : The time of the year to mark the beginning of summer, it is also the longest day of the year and the shortist night. The Summer Solstice is marked every June 21.
Winter Solstice : The time of the year to mark the beginning of Winter. It's also the shortest day of the year, and the longest night. The Winter Solstice is marked on December 21.
The Vernal Equanox: The time of year that marks the beginning of Spring. It's when the days are about even. This day happens about March 20 in the northern Hemisphere and September 22 in the southern Hemisphere.
The Autumnal Exquanox : The time of year that marks the beginning of Fall. It's the time of year that night and day are exactly even. This time of the year happens on September 22 in the northern hemosphere, and March 20th in the southern hemosphere.
These are the 4 Sabbats. You can ask about them to about anyone.
One would have to specify the culture before saying that those were the main Sabbats.
There is evidence that both the summer and winter solstice were celebrated in many cultures going back thousands of years. These were easily predicted and could be marked by such methods as the stone rings of Western Europe and certain passage graves.
There is no evidence of which I am aware to suggest that the equinoxes were celebrated by ancient societies, possibly because, unlike the solstices, it was much more difficult to determine when the equinox would fall.
The Celts however did not appear to celebrate either the solstices nor the equinoxes. All surviving evidence showed that the Celts celebrated the cross-quarter days of Beltane, Lughnassad, Samhain, and Imbolc. And the majority of what we know about the Celts centers around Beltane and Samhain.
When Gerald Gardner initially formulated what is now known as British Traditional Wicca, the only Sabbats that were celebrated with the cross-quarters, which became known as the Greater Sabbats.
However, Gardner was well acquainted with Ross Nichols who founded the Order of Bards, Ovates and Druids (OBOD). Nichols' group was celebrating the solstices and equinoxes. So Gardner decided to add those four celebrations to Wiccan practice, calling them the Lesser Sabbats.
Put altogether the eight Sabbats make up the Wheel of the Year in Wiccan practice.
