I’m posting it here both for the interest and because I have cited P52 in discussing the dating of the Gospel of John with various classes. Just a few points:
1) In my own defense (and that of others who use it), I have always pointed out the potential error in paleographic dating, and used the +/-50 years figure as an approximation. Thus I would have always pointed out that P52 could be as late as 175 CE. It appears possible it could be even later. On the other hand it could be somewhat earlier, even with the evidence cited in this article. Think of a 100 year window moving forward or backward. One might say 2nd century. In fact, I suppose one has!
2) One should also consider that the likelihood that one has laid hands on the earliest copy of a work ever produced is unlikely. So while the gospel cannot have been written after it was produced, it also was not likely written at the same time. A date of 150 or 175 CE would imply some distribution of the gospel at that point. Unfortunately, this amount of time is inherently unknowable. Still, I think it suggests that trying to date the book at or about the time a copy was produced is also questionable.
3) The article also illustrates the considerable problem with dating a small fragment, which simply compounds all of the difficulties involved in paleographic dating. With only a small amount of text to work with, one has difficulty finding sufficient data points to narrow down the result.
Still, the article is totally fascinating!