All except the Dominical letters are key letters used to translate dates within the solar calendar into a date within the synodic lunar month. On calendar key letters in general, see von Sickel 1861, and Jones 1939, 108-110; for discussion of Bede's approach to key letters, and Abbo of Fleury's elaboration of key letters into the form found in MS 17, see Calendar Overview.
MS 17 is remarkable in the manner in which it provides an interpretive table for every key letter used in the calendar (except the Golden Numbers, which require no table), and in the fact that the tables appear in the same order as the columns. Moveover, when one compares MS 17 to approximately contemporary English computi, one notices that even amongst closely related Byrthferthian-Abbonian manuscripts such as the Winchcombe computus, MS 17 is exceptional in having all eight Abbonian key letter sequences (unfortunately, there is no surviving calendar in the other major representative of this type, the Peterborough computus). Computus manuscripts of the Winchester type such as Cambridge, Corpus Christi College 391, or Cambridge, Trinity College R.15.32, or the Missal of Robert of Jumièges, tend to be very sparing in their use of key letters (usually just Dominical letters, litterae punctatae and the AEIOV series). Manuscripts of the Leofric-Tiberius type, such as British Library Cotton Julius A.VI, British Library Cotton Tiberius B.V, or Cambridge University Library Kk.5.32 are fairly generous in including key letter series. However, none of these, not even the Winchcombe computus, has the A-V, A.-I. series found in MS 17; most (including Winchcombe) are also missing the A-V sequence. Interestingly, the sequence of key letters in Winchcombe matches those in Cambridge, St John's College I.15. Winchcombe and Cambridge share graphic glosses to Bede's De temporum ratione with each other and with MS 17. Winchcombe's calendar (as discussed in Calendar Overview) is very like MS 17's and Baker and Lapidge have argued that Winchcombe is a close copy of Byrhtferth'scomputus manuscript. But the Winchcombe calendar has evidently been subjected to other influences than those which exerted themselves on MS 17.
4. CALENDAR: 9. KEY LETTERS OVERVIEW
See other months
February
March
April
May
June
July
August
September
October
November
December
fols. 16r-21v
Edition:Baker and Lapidge 1995, 390-416.
Related Manuscripts:- Winchcombe computus
Scribe:B and A,
The key letters used in MS 17's calendar, reading from the date column outwards (i.e. to the left) are:
All except the Dominical letters are key letters used to translate dates within the solar calendar into a date within the synodic lunar month. On calendar key letters in general, see von Sickel 1861, and Jones 1939, 108-110; for discussion of Bede's approach to key letters, and Abbo of Fleury's elaboration of key letters into the form found in MS 17, see Calendar Overview.
MS 17 is remarkable in the manner in which it provides an interpretive table for every key letter used in the calendar (except the Golden Numbers, which require no table), and in the fact that the tables appear in the same order as the columns. Moveover, when one compares MS 17 to approximately contemporary English computi, one notices that even amongst closely related Byrthferthian-Abbonian manuscripts such as the Winchcombe computus, MS 17 is exceptional in having all eight Abbonian key letter sequences (unfortunately, there is no surviving calendar in the other major representative of this type, the Peterborough computus). Computus manuscripts of the Winchester type such as Cambridge, Corpus Christi College 391, or Cambridge, Trinity College R.15.32, or the Missal of Robert of Jumièges, tend to be very sparing in their use of key letters (usually just Dominical letters, litterae punctatae and the AEIOV series). Manuscripts of the Leofric-Tiberius type, such as British Library Cotton Julius A.VI, British Library Cotton Tiberius B.V, or Cambridge University Library Kk.5.32 are fairly generous in including key letter series. However, none of these, not even the Winchcombe computus, has the A-V, A.-I. series found in MS 17; most (including Winchcombe) are also missing the A-V sequence. Interestingly, the sequence of key letters in Winchcombe matches those in Cambridge, St John's College I.15. Winchcombe and Cambridge share graphic glosses to Bede's De temporum ratione with each other and with MS 17. Winchcombe's calendar (as discussed in Calendar Overview) is very like MS 17's and Baker and Lapidge have argued that Winchcombe is a close copy of Byrhtferth'scomputus manuscript. But the Winchcombe calendar has evidently been subjected to other influences than those which exerted themselves on MS 17.