The view of Mac Airt and Mac Niocaill in their 1983 edition of AU that the annals of f 12–14 of TCD 1282 are indeed part of the Annals of Ulster has recently been vindicated. Analysis of the chronological apparatus of f 12–14 reveals that their author was responsible for the introduction of Dionysiac epacts and continuous Anno Domini into the Irish annals. He accomplished this by an extraordinary series of interpolations into the pre-Palladian section of the Iona Chronicle that he used as source, demonstrating both his computistical skill and profound indifference to historical chronology. By AD 431 his apparatus was accurately synchronised with all the Dionysiac chronological criteria, and he continued with it, re-ordering many events through the fifth and sixth centuries. In the seventh century he omitted a single kalend, which put all his subsequent apparatus in arrears by one year. Collation of AU with the other annals indicates that his compilation continued to c.1019 and was completed shortly after 1022. This compilation is identified with AU’s ‘Liber Cuanach’, and Cuan hua Lothcháin (†1024) is proposed as the author.