The Written Period
Within a decade or so, the gospels were starting to be written down. (The letters, of course, were written right way.) The main issue here is was is called the "Synoptic Problem," how can Matthew, Mark, and Luke be so similar and yet different in places. And what about John? The keys to the question lie in Luke 1:1-4 and John 20:30-31. There are two fundamental answers to the question. (1) The historical situatrion can be reconstructed with a high degree of certainty, and once seen many of the issues fall away. (2) Harmonization is the process by which we understand how divergent accounts can also both be accurate.