This information places Alexandrinus later than the time Jerome was translating the NT for the Vulgate (c. 392 A.D.). This will be important, when we later consider other manuscripts with the same palaeographic features.'As with Codex Sinaiticus, little doubt surrounds the date of Alexandrinus. Kenyon, followed by the overwhelming majority of textual critics, dated the MS to the first half of the 5th century. (15) Since the codex contains the works of Eusebius (d. 340 A.D.) and Athanasius (d. 373 A.D.) it cannot be dated any earlier than the 2nd half of the 4th century. (16) A date in the first half of the 5th century, however, allows enough time for the works of Eusebius and Athanasius to attain the authoritative status necessary for their inclusion in a biblical MS. (17) To place the terminus ad quem of Alexandrinus later than the 5th century, however, is "to ignore the evident signs of age and primitive simplicity which it bears in comparison with other Uncial MSS." (18)
15. Kenyon, Codex Alexandrinus, 8.
16. Specifically, we have Athanasius' Epistle to Marcellinus on the Psalms. We also have Eusebius of Caesarea's Hypotheses (i.e. table of contents) of the Psalms, and his Canons of the Morning and Evening Psalms that precede the Psalter (including Psalm 151). Fourteen liturgical canticles also follow the Psalter. See T.C. Skeat, The Codex Sinaiticus and the Codex Alexandrinus (2nd. ed. Oxford U. Press, 1955), p. 35.
17. Skeat, Codex Sinaiticus, 36.
18. Kenyon, Codex Alexandrinus, 8.
Juan Hernandez, Scribal Habits and theological influences in the Apocalypse: the singular readings of Sinaiticus, Alexandrinus, and Ephraemi (MS, 2006)