The Julian Calendar and the Problem of the Equinoxes in the Early Middle Ages
This chapter familiarizes readers with the ancient back-story of the Julian calendar and describes how one of the central problems inherent in this calendar—the drift of the equinoxes and solstices caused by an overestimation of the length of the tropical year—manifested itself in medieval literature until the end of the eleventh century. It also explores how the development of the computus genre in seventh-century Ireland was instrumental in preserving knowledge of the Western calendar’s Roman-pagan roots. The final two sections show how the existence of diverging traditions for the dates of the equinoxes and solstices in the Julian calendar created an important context for the practice of solar astronomy in early medieval Europe, which included the use of observational methods.