The Reckoning of Time

The Reckoning of Time (Latin: De temporum ratione) is an Anglo-Saxon era treatise written in Medieval Latin by the Northumbrian monk Bede in 725. The treatise includes 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.

The Reckoning of Time describes a variety of ancient calendars, including the Anglo-Saxon calendar and the Julian calendar. The focus of De temporum ratione was calculation of the date of Easter, for which Bede described the method developed by Dionysius Exiguus. De temporum ratione also gave instructions for calculating the date 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.

Bede based his reasoning for the dates on the Hebrew Bible. The functions of the universe and its purpose are generally referenced by scripture. According to the introduction by Faith Wallis in the 1999 English translated edition of The Reckoning of Time, Bede aimed to write a Christian work that integrated the astronomical understanding of computing with a theological context of history. The book is also regarded by Bede to be a sequel to his works The Nature of Things and On Time.

The work is divided into six sections:

This section familiarizes the reader with terminology regarding measurements.

In chapter 3 Bede defines a day as being 12 hours long. An hour consists of increments of puncti, partes and mementa. Each of which are small increments of time within the hour. The smallest increment of time is the atom.

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