Dating and authorship of the gospels
On the issue of dating I don't think you can really say anything is set in stone.It's literally guesswork as to when they were written, mostly based on internal evidence and examination on the writing styles and theological development of the Evangelists. And by settled I mean "we don't know who the authors were" rather than positively identifying candidates for them.About the only thing that seems fairly certain is that they were not disciples or "eyewitnesses" to the ministry of Jesus.To quote from Ehrman 1997 (recommended reading for this subreddit's wiki):(On Mark) "We do not know who the author was, only that he was a Greek-speaking Christian, presumably living outside of Palestine, who had heard a number of stories about Jesus." (p.
What we do know for a fact—admitted even by the Catholic Encyclopedia—is that the titles attached to the gospels, "The Gospel According to Matthew," etc., are not original to the texts but were added later.56)"We do not know the name of its author: the title found in our English versions ("The Gospel according to Matthew") was added long after the document's original composition" (p.79)Luke's authorship was shown to be in serious doubt in the seminal Cadbury 1920 book.98)Ehrman 1997 also spends further time discussing some of the other aspects of Lukan authorship (whether he was a companion of Paul's and the "we" passages).
And he also has some things to say towards the end of Ch. Like that the Evangelists are all fluent Greek speakers, but the disciples were probably native Aramaic speakers and Greek for them would probably have been a 2nd or 3rd language.
As one glaring example of this detachment, it is claimed that Matthew was recording events he himself had witnessed, but the gospel attributed to him begins before he had been called by Jesus and speaks of Matthew in the third person….