We say “earliest Christian Apocrypha” because there are Christian Apocrypha that are products of every period of church history, including ours. Arguably, the most influential writing of the 13th century was Voragine’s Golden Legend, a retelling of the lives of the saints, much of it based on the ancient Christian Apocrypha. Edgar Goodspeed wrote an important volume (Modern Apocrypha [Boston: Beacon Press, 1956]), as did Per Beskow (Strange Tales About Jesus [Minneapolis: Fortress Press, [1979]). Unfortunately, both are out of print.

Discussions of the dating of these documents and other technical matters are in Wilhelm Schneemelcher, New Testament Apocrypha, trans. R. McClain Wilson, 2 vols. (Philadelphia: Westminster Press, 1991); and J.K. Elliott, The Apocryphal New Testament (Oxford: Clarendon Press, 1993).