other · 367 · Alexandria
Alexandria calculated the date of Easter for the whole church and its bishop announced it in an annual festal letter. In 367 Athanasius used the letter for something else as well. He set out which books are canonical and are to be read, and the list he gives is the New Testament as it now stands: four gospels, Acts, the seven catholic epistles, fourteen of Paul including Hebrews, and Revelation. Nothing is added and nothing is missing. He distinguishes those from books that may be read for instruction — the Didache, the Shepherd of Hermas, which this dataset holds under its own event — and from apocrypha he says nobody should touch. No earlier list matches, Eusebius a generation before was still reporting the disputed books as disputed, and no council would say it in writing for decades. That an aside in a letter about a date should be the first is the sort of thing this dataset exists to record.
To tell the churches of Egypt when to keep Easter, as the bishop of Alexandria did every year.
The first list, anywhere, of exactly the twenty-seven books of the New Testament — no more and no fewer.