At the time Bede wrote the "Historia Ecclesiastica", there were two common ways of referring to dates. One was to use indictions, which were 15-year cycles, counting from 312 AD. There were three different varieties of indiction, each starting on a different day of the year. The other approach was to use regnal years—the reigning Roman emperor, for example, or the ruler of whichever kingdom was under discussion. This meant that in discussing conflicts between kingdoms, the date would have to be given in the regnal years of all the kings involved. Bede used both these approaches on occasion but adopted a third method as his main approach to dating: the "Anno Domini" method invented by Dionysius Exiguus. Although Bede did not invent this method, his adoption of it and his promulgation of it in "De Temporum Ratione", his work on chronology, is the main reason it is now so widely used. Beda Venerabilis' Easter table, contained in "De Temporum Ratione", was developed from Dionysius Exiguus' famous Paschal table.