 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 included 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 . 
