Bede - Works On Historical and Astronomical Chronology

Works On Historical and Astronomical Chronology

De temporibus, or On Time, written in about 703, provides an introduction to the principles of Easter computus. This was based on parts of Isidore of Seville's Etymologies, and Bede also include a chronology of the world which was derived from Eusebius, with some revisions based on Jerome's translation of the bible. In about 723, Bede wrote a longer work on the same subject, On the Reckoning of Time, which was influential throughout the Middle Ages. He also wrote several shorter letters and essays discussing specific aspects of computus.

On the Reckoning of Time (De temporum ratione) included an introduction to the traditional ancient and medieval view of the cosmos, including an explanation of how the spherical earth influenced the changing length of daylight, of how the seasonal motion of the Sun and Moon influenced the changing appearance of the New Moon at evening twilight, and a quantitative relation between the changes of the Tides at a given place and the daily motion of the moon. Since the focus of his book was calculation, Bede gave instructions for computing the date of Easter and the related time of the Easter Full Moon, for calculating the motion of the Sun and Moon through the zodiac, and for many other calculations related to the calendar. He gives some information about the months of the Anglo-Saxon calendar in chapter XV. Any codex of Bede's Easter cycle is normally found together with a codex of his "De Temporum Ratione".

For calendric purposes, Bede made a new calculation of the age of the world since the creation, which he dated as 3952 BC. Due to his innovations in computing the age of the world, he was accused of heresy at the table of Bishop Wilfrid, his chronology being contrary to accepted calculations. Once informed of the accusations of these "lewd rustics," Bede refuted them in his Letter to Plegwin.

In addition to these works on astronomical timekeeping, he also wrote De natura rerum, or On the Nature of Things, modelled in part after the work of the same title by Isidore of Seville. His works were so influential that late in the 9th century Notker the Stammerer, a monk of the Monastery of St. Gall in Switzerland, wrote that "God, the orderer of natures, who raised the Sun from the East on the fourth day of Creation, in the sixth day of the world has made Bede rise from the West as a new Sun to illuminate the whole Earth".