It was only in the time of Colmán, the third Ionan monk elected Bishop of Northumbria, that the conflict required royal attention and resolution.
An important figure in the convocation of the synod was Alchfrith, Oswiu's son and sub-king in Deira.
Early Christians had probably originally celebrated Easter concurrent with the Jewish Passover (see Passover, Christian holiday), which was held on the fourteenth day of the first lunar month of the Jewish year, called Nisan, the day of the crucifixion according to John .
Stephen's text has found more criticism, and Reginald Poole identified many of his inaccuracies, but Stephen's account of the synod did not suffer the same criticism as other passages in his work.
Christianity in Britain during the seventh century existed in two forms distinguished by differing liturgical traditions, labelled the "Ionan" and "Roman" traditions.
Both accounts basically agree, though Bede gives a much lengthier discourse on the debate.
The description of the proceedings, where King Oswiu presides and rules but does not engage in the ecclesiastics' debate himself, parallels examples of other synods in other sources, such as one in the Vita Sancti Bonifati by Willibald (where King Ine of Wessex performed the same function as Oswiu).
Calculating the proper date (computus) was a complex process (involving a lunisolar calendar), and different calculation tables developed which resulted in different dates for the celebration of Easter.
In the 660s, Ionan adherents chose to continue using the 84-year Latercus cycle invented by Sulpicius Severus c. Meanwhile, the Papal Curia had commissioned the Aquitanian scientist Victorius (AD 457) and later Dionysius Exiguus (AD 525) to produce a new reckoning in order to sort out the differences between the Roman and scientifically superior Alexandrian Church.About AD 600 Columbanus wrote to Pope Gregory I : "You should know that Victorius has not been accepted by our teachers and by the old Irish experts and by the mathematicians most skilled in the calculation of the computus, but was considered more worthy of ridicule and pity than of authority." Although, in Ireland, too debate raged over the best option for calculating the date of Easter.Was it better to be on the inside in accepting a dating system that brought the celebration of Easter into line with the rest of the church but one that did not hold up to scientific scrutiny?The "Ionan" practice was that of the Irish monks who resided in a monastery on the isle of Iona (a tradition within "Celtic Christianity"), whereas the "Roman" tradition kept observances according to the customs of Rome.In the kingdom of Northumbria, these two traditions coexisted, and each had been encouraged by different royal houses.Nevertheless, the Victorian table was accepted widely outside of the Irish world.