Time and theology are the twin pillars on which this thesis rests. It will explore how different scriptural interpretations led to theological and computistical differences between the Insular and continental/Roman churches. The Insular Church believed in and strictly adhered to the tradition passed on to them by their "fathers". What were the origins of these traditions and the theology that formed them? To apprehend Easter controversies, whether it is the early Quartodeciman controversy or the controversy in the Insular Church, an understanding of how biblical exegesis and different theological perspectives shaped the minds and hearts of those involved, is necessary. The Exodus story as portrayed in the Old Testament formed the basis for a theological interpretation of the Christian Passover, inheriting from Judaism a rich heritage of images and symbols used and developed in early paschal homilies. To gain insight into this particular theology the writings of those directly involved in the Insular controversy will be explored. Medieval monasteries distinguished between festal time and ordinary time. It is against this sense of "festalism" and the passionate need to get it right that the dating of Easter is argued. The discussion hinges on a fixed point of reference for the Easter full moon. The cultural sensitivies of the time must be taken into account. To celebrate "out" of time was to break the unity of the Church. More importantly, it raised the question of one's eternal salvation. Monastic life, which strongly influenced the early Irish Church was in a very real sense caught up in the great "drama" enacted between heaven and hell in which the cycle of the Christian year was a vital weapon. To date scholarly research has approached this topic from a medieval historical perspective. It has, however, never been approached from a purely theological stance. Questions regarding the Insular 84-year cycle have occupied scholars over the past one hundred years or so. A review of the literature reveals an advance in understanding the techniques of the computus of the Insular church. The work of Dáibhí Ó Cróinín is well documented and his findings have considerably enriched the body of knowledge on this question. The discovery in Padua of a latercus provided for the first time an example of an Irish computus. Accompanying this text was the text of the Paschal Canon of Anatolius: this text is essential to an understanding of the Insular computus. Anatolius' contribution was not simply technical but he provides valuable insight into the cosmological considerations behind a theological understanding of the Easter feast as a feast of light.