It's the memorial of Saint Polycarp today. He is really important for those who seek authenticity. You see Polycarp is said to have known John in his youth and Irenaeus in his old age. For the early church that was important. For many, the claim that our Bible really is the bible rests very much on the authority of Irenaeus.
No matter how you count the years it's quite a stretch. Jesus dies around 30 AD, Polycarp is said to have been converted by John around 80 AD and Irenaeus's book Against Heresies appears around 180 AD. It's possible but just. You can see why portrayals of John with Jesus always show him as a young man, so much so that he comes across looking quite girlie. Both men have to have met their mentor when they were very young and then lived long lives.
I think the reaching for authority shows a lack of faith. Irenaeus grew up in the town of Polycarp and that should be enough.
That brings me back to the apocrypha. The canon was assembled quite late and the Christians actually had their old testament canon before the Jews settled on their Bible canon. When the Rabbis left out some books that the Christians had put in, that caused some loss of confidence. Jerome didn't exclude the books we now think of as apocryphal but he did set them aside a bit. It was Protestants who later took them right out.
That's an odd thing if you think about it: Protestants in the Renaissance decided that the authority of Rabbis who didn't believe that Jesus was the Messiah should carry more weight than early Christians who did believe!
The same contradictions hold when modern Christian scholars concede the point to Jewish scholars who claim that the Gospel writers didn't understand Isaiah. The correct answer to them is that just as Kant could say he understood Plato better than Plato did himself, so too the authors of the Gospels understood Isaiah better than Isaiah did.