The Two Easters

The substance of the dispute that ended St. Colmán’s Northumbrian episcopate was a problem in calendrical astronomy: how to fix the date of Pascha. The Insular churches of Iona and Lindisfarne computed Easter by an older 84-year cycle (the latercus) with one set of lunar limits and equinox; the party advancing the Alexandrian-Roman reckoning used the 19-year (Dionysiac) cycle with another. Because the two systems could diverge in any given year, Easter — and with it the end of the Lenten fast — could fall on different Sundays for Christians living under one roof. This file explains the computus accurately and accessibly, marks where modern scholarship reconstructs the Insular cycle and where it remains uncertain, and reads the famous Northumbrian case of a feasting king and a fasting queen.

Tradition: Pan-Orthodox (pre-Schism; Celtic; defender of the Celtic Pascha)

Why Pascha Needs Computing at All

The date of Pascha is not fixed to a single day of the solar calendar, the way the Nativity is fixed to 25 December, but is calculated each year from a rule inherited ultimately from the Jewish Passover and refined by the early Church: it is the first Sunday after the first full moon on or after the spring equinox (Corning 2006, 1–18; on the Orthodox reckoning, see The Church Calendar). That rule sounds simple, but every term in it requires a definition that the ancient and early-medieval Church did not at first hold in common. Which equinox — the true astronomical one, observed, or a conventional calendar date? On which day may the Paschal full moon fall, and within what range of the lunar month must Easter Sunday itself be kept? And how is the moon’s age to be tracked across the years, given that twelve lunar months fall about eleven days short of a solar year, so that the lunar and solar calendars drift against each other and must be reconciled by a repeating cycle? (Corning 2006, 7–17; Charles-Edwards 2000, 391–415.) The body of rules and tables that answered these questions is the computus, and the differences between the Insular and the Alexandrian-Roman answers are the whole of the paschal controversy on its technical side (Bede, HE III.25; trans. Colgrave & Mynors 1969).

It is essential to state at the outset what kind of disagreement this is. Both sides accepted the same Nicene principle — that Pascha is a Sunday feast, computed from the equinox and the moon, kept by the whole Church in unity, and distinguished from the Jewish Passover (Corning 2006, 18–30). The quarrel was over the implementation of an agreed rule, not over the rule’s meaning or any article of faith. Bede, our chief source, never accuses the Irish of heresy; he charges them with error in computation and with obstinacy in clinging to it (HE III.25, V.21; Colgrave & Mynors 1969; Stancliffe 1995). That distinction governs everything that follows.

The Three Variables

Three components of the computus diverged between the traditions, and it is their combination that produced different Easters.

First, the length of the cycle. Because the lunar and solar years do not divide evenly, a fixed number of years must elapse before the phases of the moon recur on the same calendar dates and the whole pattern of Easters repeats. The Insular churches used an 84-year cycle; the Alexandrian computus, transmitted to the Latin West in the tables of Dionysius Exiguus (525) and championed in Northumbria by the Roman party, used the more astronomically accurate 19-year cycle (the Metonic cycle, in which 235 lunar months almost exactly equal 19 solar years) (Corning 2006, 7–17; Mosshammer 2008, 204–243; Charles-Edwards 2000, 405–406). The 84-year cycle was the older standard in much of the Latin West before the Dionysiac reckoning displaced it; the Insular churches had received it early and kept it after Rome itself had moved on, which is why Bede can present the Roman position as the position of the universal Church of his own day (HE III.25; V.21; Corning 2006, 84–101).

Second, the equinox. The two traditions placed the spring equinox on different conventional dates. The Alexandrian reckoning fixed it at 21 March; the older Latin (and Insular) tradition associated with the 84-year cycle generally used 25 March, the conventional Roman equinox (Corning 2006, 7–10; Charles-Edwards 2000, 393–395). A later equinox can push the qualifying Paschal full moon, and therefore Easter, into a different week.

Third, and most sharply, the lunar limits. Within the lunar month — counted from luna 1 (new moon) — each tradition prescribed a range of days on which Easter Sunday was permitted to fall. The Insular reckoning allowed Easter Sunday on luna 14 to luna 20; the Alexandrian-Roman reckoning allowed it on luna 15 to luna 21 (Corning 2006, 8–17; Wallis 1999, xxxiv–lxiii; Charles-Edwards 2000, 392–393). The difference of the lower limit is the crux. Because the Insular system permitted Easter on luna 14 — the very day of the Paschal full moon, the day that could itself be the 14th of Nisan, the Passover — Bede and the Roman party charged that the Irish “sometimes” kept Easter with the Jews, in violation of the principle, which they traced to Nicaea, that Easter must follow and not coincide with the Passover (Bede, HE III.25; V.21; Colgrave & Mynors 1969; Corning 2006, 18–30). This is the heaviest of the polemical charges, and it must be read with care: the issue was not that the Irish observed the Jewish feast, but that their lunar limit allowed Easter to fall on a day the Roman reckoning reserved as too early.

The 84-Year Cycle and the Latercus

What exactly was the Insular 84-year cycle? Here the honest answer is that modern scholarship has recovered a great deal but that important features remain reconstructed rather than directly attested, and the precise form and pedigree of the Insular cycle are genuinely contested among historians of the computus.

[Disputed: the exact form and origin of the Insular *latercus* — Dáibhí Ó Cróinín, who with Daniel McCarthy reconstructed the cycle from the *Sirmond* manuscript (Oxford, Bodleian Library, MS Bodley 309) and the Padua *latercus*, identifies it as an 84-year cycle with a *saltus* (the inserted lunar leap) and a 14-year structure of distinctive design, used in Ireland and Iona (McCarthy and Ó Cróinín, "The 'lost' Irish 84-year Easter table rediscovered," *Peritia* 6–7 [1987–88], 227–242; Ó Cróinín, *Early Medieval Ireland 400–1200*, 1995, 201–204); Bede himself attributes an 84-year cycle to the Insular churches but does not transmit its tables (*HE* V.21); the older view, that the Insular churches used the 84-year *Supputatio Romana* essentially unchanged, has been substantially revised by this reconstruction, though the cycle's ultimate derivation and the security of every reconstructed value remain debated].

The cycle was known in the Insular world by the Latin term latercus, “the table” or “list,” and tradition associated the 84-year reckoning with the names of earlier Latin computists — most often Sulpicius Severus (in the Insular attribution) and Augustalis, to whom an early Latin paschal computation was ascribed (Charles-Edwards 2000, 405–408; Corning 2006, 9–12). These attributions should be reported as the tradition’s own claims rather than as established authorship.

[Disputed: the authorship and antiquity of the 84-year material — the Insular tradition attached the *latercus* to Sulpicius Severus (d. c. 425), and an "Augustalis" is named in the early Latin computistical record as author of an 84-year cycle, but whether either attribution is historically sound is uncertain; Charles-Edwards (2000, 405–408) treats the Sulpician ascription as the Insular churches' own genealogy for a cycle they had long received, while the dating and identity of Augustalis are debated in the computistical literature (Mosshammer 2008, 204–243; cf. Ó Cróinín 1995, 201–204). What is secure is that the Insular churches used an 84-year cycle older than the Dionysiac 19-year one; the names attached to it carry less certainty than the cycle itself].

What can be said with confidence is structural. The 84-year cycle is less astronomically accurate than the 19-year Metonic cycle: over 84 years the assumed lunar phases drift measurably from the true moon, so that the Insular Paschal full moon could fall a day or more away from the astronomical full moon (Corning 2006, 7–17; Wallis 1999, xlvi–lxiii). Combined with the earlier permitted limit (luna 14) and the later equinox (25 March), the cycle’s drift meant that in particular years the Insular computists arrived at a different Sunday for Pascha than the Alexandrian-Roman computists did — sometimes a week earlier, occasionally more (Corning 2006, 7–17; Charles-Edwards 2000, 391–415). It is this concrete possibility of two Easters in one realm, not any abstract theory, that made the controversy urgent.

How One Year Yielded Two Easters

Put the three variables together and the mechanism is plain. Suppose a year in which the Paschal full moon, by both reckonings, falls early. Under the Insular rule, with its lower limit of luna 14 and its 25 March equinox, the computists might find the moon reaching luna 14 on a Sunday already qualifying as Easter — and keep the feast that day. Under the Alexandrian-Roman rule, with luna 15 as the earliest permitted day and 21 March as the equinox, that same Sunday is disallowed as too early, and Easter is deferred a week (Corning 2006, 7–17; Bede, HE III.25; Colgrave & Mynors 1969). In such a year the two communions would keep Pascha a week apart — and because the Great Fast runs to the eve of Pascha, the Roman party would still be fasting on the very Sunday the Insular party had already begun the paschal rejoicing (Mayr-Harting 1991, 103–113). The divergence was not every year; the cycles agreed far more often than they differed. But in the years they differed, the difference was visible, public, and pastorally intolerable to a single household or kingdom (Corning 2006, 84–101).

Bede’s Famous Notice: A King Feasting, A Queen Fasting

Bede gives the controversy its human face in a single sentence whose force every subsequent historian has felt. Recounting the situation in Northumbria before the Synod of Whitby, he records that King Oswiu, raised among the Irish of Iona and trained in their reckoning, kept Easter by the Insular cycle, while his queen, Eanflæd — daughter of Edwin of Northumbria but raised in Kent and instructed by the Roman missionary tradition through her chaplain Romanus — followed the Roman computus. The consequence, Bede writes, was that “it sometimes happened in those days that Easter was celebrated twice in the same year, so that the king had finished the fast and was keeping Easter Sunday, while the queen and her people were still in Lent and observing Palm Sunday” (Bede, HE III.25; trans. Colgrave & Mynors 1969). The image is exact: under one roof, at one court, the king sat at the paschal feast while the queen kept the most solemn week of the fast.

Bede deploys the anecdote to dramatize the scandal of disunity and to motivate the synod he is about to narrate, and his framing is that of a Roman partisan for whom the situation is self-evidently an embarrassment to be resolved in the Roman direction (Mayr-Harting 1991, 103–113; Stancliffe 1995). The historian must register both the value and the slant of the testimony: the value, because the detail is circumstantial, early, and tied to a named royal household; the slant, because Bede chooses, shapes, and weights it to serve the argument that conformity was necessary (on Bede’s narratorial control, see Bede as the Narrator; on his rhetoric, The Rhetoric of the History). What is not in doubt is the underlying calendrical fact: the two computes could, and in Northumbria did, place Pascha on different Sundays, with the end of Lent following the feast — and that this affected real people at the highest level of the kingdom is the strongest single demonstration that the dispute, though technical, was not academic (Bede, HE III.25; Colgrave & Mynors 1969; Corning 2006, 84–101).

“Not With the Jews”: The Heaviest Charge

The principle that Pascha must not be kept with the Jewish Passover was, by the seventh century, common ground in both traditions; the Insular churches did not dispute it (Corning 2006, 18–30; Charles-Edwards 2000, 392–393). What the Roman party charged was that the Insular lunar limit permitted Easter on luna 14, the day that could coincide with 14 Nisan, and so risked keeping the feast with the Jews in violation of the agreed rule (Bede, HE III.25; V.21; Colgrave & Mynors 1969). The Irish reply — preserved obliquely through Bede — was that they too forbade keeping Pascha with the Jews and that their luna 14 limit, rightly applied, did not in fact do so, since their rule still required a Sunday and the equinox condition (Corning 2006, 18–30; Charles-Edwards 2000, 392–395). The two sides were arguing about whether the Insular system, in operation, ever broke a rule both accepted — a dispute about the consequences of a calculation, not about the principle. Bede, vindicating the Roman outcome, presents the charge in its strongest form; the modern reader should hold it as a contested technical accusation, not a settled fact of Irish practice (Stancliffe 1995; on the principle in Orthodox tradition, The Church Calendar).

What the Computus Was and Was Not

The two Easters were a real and painful problem of order, and nothing more than that. No article of the Creed turned on the choice of cycle; no sacrament was invalid under either reckoning; the Christology and faith of the Insular churches were the catholic faith (Mayr-Harting 1991, 103–113; and see The Tonsure and Other Customs). The computus is a discipline of the Church’s time-keeping — a matter of when the one feast is kept, not of what the feast is. That St. Colmán defended the older cycle does not make him a man of error in faith; it makes him the conservator of a venerable Insular practice that the wider Church, for the sake of unity, was in the end persuaded to set aside (Bede, HE III.25–26; Colgrave & Mynors 1969; and see What Was Really at Stake). The decision belongs to the next sections; the substance belonged here.

References

Bede. The Ecclesiastical History of the English People (Historia Ecclesiastica gentis Anglorum). Ed. and trans. Bertram Colgrave and R. A. B. Mynors. Oxford Medieval Texts. Oxford: Clarendon Press, 1969. (The paschal controversy and the Oswiu–Eanflæd notice — Easter kept twice in one year — at III.25; the Synod of Whitby at III.25; Ceolfrith’s letter to King Nechtan on the computus, the 84-year cycle, the lunar limits, and the equinox at V.21.)
Corning, Caitlin. The Celtic and Roman Traditions: Conflict and Consensus in the Early Medieval Church. New York: Palgrave Macmillan, 2006. (The components of the computus; equinox dates; lunar limits luna 14–20 vs 15–21; the “not with the Jews” principle; the Northumbrian situation.)
Charles-Edwards, T. M. Early Christian Ireland. Cambridge: Cambridge University Press, 2000. (The Insular 84-year cycle; the Sulpician attribution; the lunar and solar reconciliation; pp. 391–415.)
Mayr-Harting, Henry. The Coming of Christianity to Anglo-Saxon England. 3rd ed. University Park: Pennsylvania State University Press, 1991. (Oswiu and Eanflæd; the pastoral and political stakes of the divided Easter; pp. 103–113.)
McCarthy, Daniel, and Dáibhí Ó Cróinín. “The ‘lost’ Irish 84-year Easter table rediscovered.” Peritia 6–7 (1987–88): 227–242. (Reconstruction of the Insular latercus from the Sirmond and Padua tables.)
Ó Cróinín, Dáibhí. Early Medieval Ireland 400–1200. London: Longman, 1995. (The latercus and the Insular Easter tables; pp. 201–204.)
Mosshammer, Alden A. The Easter Computus and the Origins of the Christian Era. Oxford: Oxford University Press, 2008. (The 84-year and 19-year cycles; Augustalis; the Dionysiac reckoning; pp. 204–243.)
Wallis, Faith, trans. Bede: The Reckoning of Time (De temporum ratione). Translated Texts for Historians 29. Liverpool: Liverpool University Press, 1999. (The mechanics of the computus, lunar limits, and the saltus lunae; introduction, pp. xxxiv–lxiii.)
Stancliffe, Clare. “Oswald, ‘Most Holy and Most Victorious King of the Northumbrians.’” In Oswald: Northumbrian King to European Saint, ed. Clare Stancliffe and Eric Cambridge. Stamford: Paul Watkins, 1995. (Bede’s partisanship and the Insular reckoning.)