Read Wheel of the Year - Wikipedia (en.wikipedia.org)

The Wheel of the Year is an annual cycle of seasonal festivals, observed by many modern Pagans, consisting of the year's chief solar events (solstices and equinoxes) and the midpoints between them. While names for each festival vary among diverse pagan traditions, syncretic treatments often refer to the four solar events as "quarter days" and the four midpoint events as "cross-quarter days", particularly in Wicca. Differing sects of modern Paganism also vary regarding the precise timing of each celebration, based on distinctions such as lunar phase and geographic hemisphere.