Adomnán, in keeping with Ionan tradition, made several more trips to the lands of the English during his abbacy, including one the following year. It is sometimes thought, after the account given by Bede, that it was during his visits to Northumbria, under the influence of Abbot Ceolfrith, that Adomnán decided to adopt the Roman dating of Easter that had been agreed some years before at the Synod of Whitby. Bede implies that this led to a schism at Iona, whereby Adomnán became alienated from the Iona brethren and went to Ireland to convince the Irish of the Roman dating. Jeffrey Wetherill sees Adomnán's long absences from Iona as having led to something of an undermining of his authority; he was thus unable to persuade the monks to adopt the Roman dating of Easter, let alone the tonsure. It is clear that Adomnán did adopt that Roman dating, and moreover, probably did argue the case for it in Ireland.