Within each cycle of time there are four main divisions or quarters and eight major power-points or time-chakras. The power-points occur at the cusps and mid-points of the quarters, and are the manifestation in time of the eight spokes of the archetypal Wheel of Life.
In the annual cycle of time the quarters are referred to as seasons and the power-points are known as the eight great solar or fire festivals. The four power-points that divide the year into its four quarters, marking the cusps of the seasons, are known as the quarterdays. The four power-points that mark the mid-points of the seasons are called the solstices and equinoxes.*
The quarterdays, being on the cusps of the seasons, are fluid and feminine in nature, as one season flows into the next. By contrast, the solstices and equinoxes, which occur when the seasonal energy is at its most intense, are fixed and masculine in nature. This gives rise to the symbolism of the two Cosmic Crosses, masculine and feminine, erect and saltire, red and white, gold and silver, referred to in Christian tradition as the St George and St Andrew Crosses.
By celebrating these great solar festivals in sequence throughout the year we align ourselves with the alternating current of the cosmos—the feminine-masculine, yin-yang wave effect of the universal life force—and thereby are not only stimulated by it but also help to maintain the right balance and harmony of the polarities of life as they manifest in the world.
An analogy can also be made with surfing, wherein the solar festivals are the mega-waves that all good surfers seek to ride. They occur at approximately six to seven-week intervals.
*A purely mathematical division of a 365-day year would place the power-points on the 21/22 December, 5 February, 23 March, 8 May, 22 June, 6 August, 21 September, and 5 November; but, as the annual circuit of the earth around the sun is not quite so exact in its number of days (e.g. we need to add an extra day to the year every four years), and the timing of the quarterdays is somewhat fluid, the dates vary slightly from year to year.