“For this book helped to establish the custom of counting years from the birth of Christ. When we say that Queen Elisabeth II was born in 1926 (not ‘in the 16th year of the reign of George V’, or ‘in the year 2678 after the foundation of Rome’, or in the year after the 481st Olympiad’), we are indebted to the Venerable Bede.” (PMM p. 16)

In Anglo-Saxon England during the mid-7th century, there was a ambition to separate the timing of Easter from the Jewish Passover calendar and to ensure its observance on a Sunday.
Following in the footsteps of Christian scholars before him who delved into the issue of determining the correct date for Easter, Bede, in 725, aimed to clarify the ecclesiastical rationale behind the Synod of Whitby's 664-decision, which favored Roman customs over Irish practices.

“The Reckoning of Time is about measuring time and constructing a Christian calendar, or what later medieval writers called computus. It is the earliest comprehensive treatment of this subject, for though there was an abundant calendar literature before Bede’s day, it was both fragmentary and partisan in character. (…) Bede’s book is very different in form and content. Although he is also the partisan of one form of Paschal table – the Alexandrian 19-year cycle, as elaborated by Dionysius Exiguus – he sought to establish its credibility by making it the basis of a comprehensive manual of time reckoning. It was a gamble that paid of. So lucid, thorough and well organized was Bede’s exposition, so easy was it to teach from and learn from, that it can be said to have not only guaranteed the ultimate success of Dionysius’ system, but to have made computes into a science, with a coherent body of precept and a technical literature of its own.” (Faith Wallis. Bede the Reckoning of Time).’.

The editio princeps was published in 1505.