Manuscripts
Manuscript:
Padua, Biblioteca Antoniana, MS I.27
  • s. xin
Mc Carthy, Daniel P., “The chronology of Saint Columba’s life”, in: Moran, Pádraic, and Immo Warntjes (eds), Early medieval Ireland and Europe: chronology, contacts, scholarship. A Festschrift for Dáibhí Ó Cróinín, Studia Traditionis Theologiae 14, Turnhout: Brepols, 2015. 3–32.  
abstract:
Between Adomnán’s Vita Columbae and Bede’s account in his Historia ecclesiastica, Saint Columba’s life and missionary career are the best recorded of all early Irish ecclesiastics. Further, and in great contrast to his 5th-century British missionary predecessor, Saint Patrick, Columba’s chronology has not been the subject of controversy in modern times. At least from the 17th-century scholarship has been almost unanimous that Columba died in AD 597, a date that derives from Adomnan’s assertion that he died on Sunday, and that he left Ireland in AD 563, which likewise derives from Adomnán’s statement that his mission had lasted 34 years. However, Dáibhí Ó Cróinin’s identification in 1985 that Padua, Biblioteca Antoniana, I 27, 76r-77v preserves a copy of the paschal table followed by the early Irish church demonstrated that the feria of the kalends of January was the primary chronological criterion used by early insular Christian scholars to identify each successive year. It was this discovery that prompted examination of the ferial data preserved in the Clonmacnoise group of Irish annals, which in turn revealed that annals were compiled contemporaneously with Columba’s life, and hence that the annalistic account of Columba predates those of Adomnán and Bede by a century. These ferial data locate Columba’s obit unmistakeably at AD 593, and this four-year discrepancy raises serious doubt regarding the veracity and honesty of Adomnán’s account of Columba’s life.
Mc Carthy, Daniel P., “On the arrival of the Latercus in Ireland”, in: Warntjes, Immo, and Dáibhí Ó Cróinín (eds), The Easter controversy of Late Antiquity and the early Middle Ages: its manuscripts, texts, and tables. Proceedings of the 2nd International Conference on the Science of Computus in Ireland and Europe, Galway, 18–20 July, 2008, Studia Traditionis Theologiae 10, Turnhout: Brepols, 2011. 48–75.  
abstract:
The hypotheses published in 1733 by van der Hagen regarding the supposed computistical parameters and Roman origin of the Latercus, the 84-year Paschal tradition followed by the early Insular churches, and the alleged forged status of Paschal tracts cited by Insular authors are profoundly mistaken when viewed beside the evidence of the copy of the Latercus discovered by Dáibhí Ó Cróinín in Padua MS I 27. Furthermore, the computistical features of this Padua copy are in accordance with Aldhelm’s attribution of the Latercus to Sulpicius Severus. Examination of references to the use of the Latercus in Ireland made by Columbanus, and others cited by Bede, together with the evidence of the synchronization of lacunae in the Irish annals with the embedded papal and Anglo-Saxon chronicles, imply that the Latercus arrived in Ireland in circa 425. Consideration of the provenance of the contemporaneous fifth-century Annalistic entries indicates that the Latercus was first established in the province of Leinster.
(source: Brepols)
Mc Carthy, Daniel P., “Easter principles and a fifth-century lunar cycle used in the British Isles”, Journal for the History of Astronomy 24 (1993): 204–224.  
abstract:
The computational principles underlying the Paschal table, or latercus, found in the manuscript Padua, Bibl. Antoniana I.27 f. 76r–77v, are closely analysed and the details of the mechansims of its embolism, bissextile and saltus are resolved as closely as possible. With this information it is possible to eliminate all of the scribal errors from the table and, thus restored, the table is presented in full. From this can be seen that the Padua latercus preserves an 84-year lunar cycle with a 14-year saltus, a lunar term from luna 14 to 20, and a Paschal term from 26 March to 23 April. Thus it emerges that this latercus is an example of the Paschal cycle known to have been employed by the British, Scots and Picts between the fifth and eighth centuries and which was at the centre of the Paschal controversy debated in Whitby in AD 664, as Bede relates in length in his Historia ecclesiastica. It is the first such example reported for over 1200 years.
(source: author)
Mc Carthy, Daniel P., and Dáibhí Ó Cróinín, “The ‘lost’ Irish 84-year Easter table rediscovered”, Peritia 6–7 (1987–1988): 227–242.