Calibrating the Annales Cambriae

The Need to Calibrate the Annales Cambriae

The Annales Cambriae (AC) are a terse record of British historical events from the fifth to the tenth centuries CE, with dates. But the dates in it are only on its own year count. It (in the “A” text) numbers years from its own year 1 to its year 533, with no mention of the CE calendar or any other calendar used elsewhere. A user of the AC therefore has to choose a calibration of its dates to years CE.


Calibration should not be uniform

Some AC entries are for events also recorded elsewhere whose dates are beyond dispute, such as the birth of St. Columba, his move to Iona, and the death of Pope Gregory. No calibration can map all of these undisputed dates neatly and exactly over the AC, not even when allowance is made for some ancient sources starting the year on 25th March and others on 1st September. The calibration most often used is +444, i.e. AC year 1 is deemed to be 445CE, year 100 is 544, and so on down to AC year 533 = 977CE. This makes sense, for it is usually regarded as the best-fit calibration for the later centuries covered by the AC.


However, it may not be wise to make a uniform calibration across the whole of the AC. Every translator of and commentator that I have ever read, prior to Gough-Cooper in 2012, converts the AC to the CE calendar by adding the same number to every AC year. As I showed, though, in my previous post here (19th September 2013), the AC is a compilation from several sources. Its compilers could have made a calibration inconsistency when meshing their sources.


On the best fit for the early years, AC Year 1 = 446CE

The best fit calibration for the AC entries for events prior to the mid-560s CE is +445. From the later 560s to at least the 630s the best-fit calibration is +442. Later, it is indeed +444. Gough-Cooper, imaginatively, endeavours to straighten the kinks by deeming the AC to have erroneously repeated the four years corresponding to 558-561CE and, perhaps influenced by McCarthy’s finding of missing years in the Irish annals when he synchronised them, he reckons the AC to have missed years elsewhere. The effect of his thorough attempts to calibrate AC dates as closely as possible with externally known dates is that his AC calibration changes frequently, wandering between +441 (in the mid-seventh century) and +448 (in the mid-sixth century).[1]


As described in my previous post here, I interpret the linguistic and geographical elements of the AC as indicating that all of its entries for events before the 530s CE and a minority of those for the period 530 to 613 originated from one source, which I suggest was Glastonbury Abbey, and that the majority of the entries for the 530-613 period were derived from other, Welsh, originals.


Dates before 529CE could not have been contemporaneously described in the AD calendar (now often called “CE” for “Common Era”), as this calendar was only invented (by Dionysius Exiguus of Constantinople) in that year. They could have been recorded by the regnal year of the Roman Emperor – though this would have been inhibited after 474CE by the demise of the Western Roman Empire; or on the Anno Mundi calendar (counting dates from the supposed creation of the world); or on a Year of the Incarnation (birth of Jesus) calendar non-identical with the AD calendar; or on a Year of the Passion calendar which started from the death of Jesus, which that calendar dated to 27 years after his birth.


Which one, or ones, might have been used at Glastonbury is not knowable. What matters is that the information from Glastonbury that the AC compilers used, particularly for events prior to 529CE, would have been calibrated to AC years independently from the data they acquired from Welsh abbeys for events that Christian monks would have registered from the beginning against AD dates. I reckon therefore that the shift in calibration in the 560s is due to an inexact meshing by the AC compilers of the dates provided by their different sources.


A +445 calibration for the early years of the AC makes it possible to make sense of a peculiar feature of the A text. The AC marked out years from its year 1 to year 533 because the Roman church’s method for the calculation of the date of Easter repeats on a 532-year cycle. So when any year is arbitrarily defined as Year 1, Year 533 is the first year of the next cycle. The last 23 years of the AC’s 533 are blank. Modern scholars say this was because these years were still in the future when the AC were completed: a fully rational cause, given the compilers’ motivation for marking out 533 years. But the first eight years are also without entries. This makes no rational sense at all: why not start by choosing for year 1 a year with an event in it, and add eight more blank future years at the time of presenting the AC to King Rhodri?


There was however a very important event in 446CE which could have inspired the AC compilers to choose it as the year 1 of the AC. It was the year in which according to St. Gildas, whom all agree is a very reliable source, the British warlord Vortigern invited English warriors led by Hengist to be mercenaries to help him defeat Irish and Scottish forces that were attacking Roman Britain. He gave Hengist sovereignty over the Isle of Thanet as his army base. Vortigern turned to Hengist for support because Aetius, the de-facto commander of Roman forces in the near Continent to whom he appealed first, was too pressed to be able to spare any military aid for Britain. Vortigern’s decision was retrospectively regarded as momentous because it was perceived as the first, or the most world-changing, of a chain of events that led to English rulers being kings over the entire arc of coastal Britain from East Yorkshire round to east Hampshire within half a century, and over most of what had been Roman Britannia by 633.


On the +445 calibration, Vortigern’s invitation to Hengist indeed happened in AC year 1. It is so recorded in the B text of the AC, with an entry that translates as “the coming of the English of Horsa and Hengist in the time of King Vortigern”. The C text has almost identical words.


It is not in the A text. But it is quite possible that it was there originally, for the corner of the manuscript where it could have been is torn off. If we interpolate that there was originally an entry for Vortigern and Hengist, and an intended +445 calibration to the CE calendar, the selection of the starting point of the AC becomes coherent.


Although a +445 calibration is the best fit for the early years of the AC, it does not result in all the entries being correctly dated. Several dates differ from ones identified elsewhere by one or two years (see Table). The variations may be due to such factors as the differences in when a new year was deemed to start, delays in reporting news or divergent interpretations of the meaning of phrases such as “December of last year”, and slippery miscopyings of Roman numerals, as well as to arithmetic errors in conversion of source data given in non-AD calendars.


Such discrepancies are not terribly important; and, besides, there is no guarantee that it is always the AC that is wrong and the English or Irish other source that is correct.


However, there are three entries for years prior to 613CE where the AC date is substantially different from that given elsewhere, and is wrong: the birth of St. Bride, the Battle of Badon, and the death of St. David. I can offer no explanation for the error on St. David, other than to presume a scribe’s mistake.[2] The date of Badon requires a substantial commentary which will be the subject of a separate post. As for the birth of St. Bride, as I explained in my post of 17th July 2013 (under the subheading “St. Columba and St. David”), a credible basis for this 16 year error in her year of birth is confusion by subsequent recordkeepers at Glastonbury Abbey between two visits she made, 16 years apart, to that holy shrine.


These mistakes apart, the AC shows a sufficiently close similarity to other sources where it can be corroborated to justify regarding it as a good source of dates – give or take a couple of years – of the events that it records where no such corroboration is possible, including those such as the Battles of Camlan and of Armterid whose existence is attested elsewhere but not their date. And I have sought to show that the AC dates should be translated to the CE calendar by adding 445 to the AC year count ticker number from the AC’s year 1 to AC118, and by adding 442 to the AC year count ticker number from the year of its next event record, AC126 until the mid-seventh century.[3]




Schedule of AC Events


Intended year CE as calibrated

Translation of entry

Actual date where one can be determined or estimated other than from the AC


Easter changed to Sunday by Pope Leo, Bishop of Rome



St. Bride was born



St. Patrick went to God



Death of Bishop Benignus



Bishop Ebur died in Christ



Battle of Badon in which Arthur carried the cross of our lord Jesus Christ for 3 days and 3 nights and the Britons were the victors



St. Columcille was born



Death of St. Bride



Strife of Camlann in which Arthur and Medraut were killed



There was mortality in Britain and in Ireland



Death of Ciaran



Great mortality in which Mailcun, King of Gwynedd died. 



Gabran son of Dungart died



Columcillae went out into Britain


568 *

Gildas died



Battle of Armterid



Brendan Byror died



Guurci and Peretur died



Battle against the Isle of Man



Dispositio for Danielus of the Bangors



Conversion of Constantinus to the Lord



Columcille died



King Dunaut died


593 (596**)

Augustinus [and] Mellitus converted the Angles to Christ

596 (601***)


Synod of Chester



Gregorius died in Christ



Bishop Dauid of Menevia



Dispositio for Bishop Cinauc



Aidan son of Gabran died



Death of Conthigirn



and [i.e. death] of Bishop Dibric



Battle of Chester where Selim of the sons of Cinan was killed and Iacob of the sons of Beli died




* Perhaps January 569. The Welsh sources for the AC may have used a 25th March New Year.


** 596 on a +445 calibration, as might be appropriate for this entry if the AC compilers took the data from a Glastonbury source. The gap in the manuscript between this entry and the other two events entered for AC year 151 could be due to those data having come from different sources.


*** According to Bede, Mellitus arrived four or five years after Augustine.

[1] Gough-Cooper ( ) gives respect to every blank year marked by “an” (for annus) in the manuscript. I regard the decade count in Roman numerals there as the reliable indicator of the intended years of events it records, to be given precedence over adding the empty an’s where these two methods conflict.


Gough-Cooper assumes that the “baptism of King Edwin” recorded in the AC is the same event as his baptism recorded by Bede. However, a different baptism of Edwin, by Rum, is recorded in the Historia Brittonum. An explanation that reconciles both the sources is that Edwin was baptised by Rum but, because Rum (a British prince of Rheged) was following the date-of-Easter custom upheld by the Celtic churches, the Roman church did not recognise that baptism as valid and Edwin allowed himself to be re-baptised by the Roman Bishop Paulinus. Bede vigorously favoured the Roman stance in the date-of-Easter controversy and therefore reported only Edwin’s baptism by Paulinus; the AC Northumbrian entries, by contrast, were written by a supporter of the Celtic side in that dispute – perhaps indeed Rum himself. Gough-Cooper also appears to have ignored McCarthy’s evidence that the correct date for St. Columba’s death is 593 and not the customarily believed 597.

[2] A note in the C text of the AC hints at the possibility that the original AC miscalculated this date. Marginalia on this manuscript in a different hand from the entry can be translated “in the year after the Incarnation of the Lord DC xlv”. 587CE is on my calibration Year 145 of the AC, i.e. Year Cxlv. It could be, therefore, that the person responsible for the insert in the C text margin had in their hand or their head both the correct date for St. David’s death and the year ticker structure of the A text, and – correctly – wrote C xlv as their calculation of the year of the AC that St. David’s death should be recorded in, but wasn’t. That a calculation was going on is shown by the writing in this marginalia of numeral letters that were crossed out. (The words “in the year after the Incarnation of the Lord” are of course out of place here.)

[3] With the exception of the conversion of the Angles to Christ.



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