Not infrequently I have described my interest in the dates at which the New Testament texts were composed as the expression of a neurotic compulsion. There is probably some truth to that, perhaps even much truth. Indeed, sometimes when I labour upon the minutiae of the data I can feel Leo Strauss' words against "pain-loving antiquarianism" rattling around in my head. But the truth is that there is more than just neurosis going on, and that precisely because--despite my ironic self-deprecation (a Canadian vice that personally I think makes us quite endearing)--I am in fact driven by more than an antiquarian impulse. As I reflect upon my own work, I increasingly realize that at the heart of my scholarly endeavours is an effort to overcome what I have in print described as the "rupture hypothesis," i.e. the hypothesis that between Second Temple Judaism and the church stands an unbridgeable chasm. Actually, there are in this hypothesis two chasms, two ruptures, such that it should perhaps be better described as the hypothesis of double rupture. The first rupture is typically situated somewhere between Judaism and Jesus (Jesus himself is often identified as the party responsible, although sometimes the Baptist comes under indictment), the second somewhere between Jesus and the church (here Paul is often trotted into the dock). Within biblical studies, these ruptures are conceptualized in various ways, all of which tend in their turn to reveal unhealed biases. Sometimes these ruptures are conceptualized in terms of a contradiction between Jewish law and Christian grace (here we confront lingering but theologically and empirically dubious suspicions that anyone who thinks legally cannot experience divine favour, and that if such a person does experience divine favour such a person will ipso facto cease and desist their legal thinking); other times it is conceptualized in terms of a contradiction between Semitic monotheism and Hellenistic theology (here we confront pernicious yet facile narratives about the Hellenization of Christianity); still other times it is conceptualized in terms of a contradiction between spontaneous charisma and sterile institution (here we confront a whole series of hard-to-kill suppositions regarding the incompatibility of spirituality and routine). But ultimately the identification of such conceptions and generally-correlated biases is not what overturns the rupture hypothesis, no matter how salutary such identification might be. Rather, what overturns the rupture hypothesis is the relevant data. And the relevant data puts to the lie this hypothesis of the double rupture. Quite simply, the data clearly demonstrates that Jesus and his followers were fully grounded in Judaism, and it equally demonstrates that the church is fully a consequence of the operations carried out by Jesus and his first followers. Modern historiography can finally apprehend this dual reality because modern historiography has developed the capacity to conceptualize change with continuity ("continuity with change" being what I would consider to be a succinct definition of development).
So, how does chronology relate to this? I would argue that a lower chronology (i.e. one that tends to date the New Testament texts earlier than the consensus dates) bridges the putative ruptures more readily than any other. The earlier that the earliest extant Christian texts were written, the more plausible it is to identify them as fully Jewish. At the same time, the earlier that the earliest extant Christian texts were written, then the earlier that we can situate the specifically Christian developments evident therein. Put more synthetically: insofar as the most foundational Christian developments occurred while Christianity was most fully within the bosom of Judaism, we are able to more fully and clearly conceive the relationship between Judaism and Christianity as one that entails continuity with change. Of course, this is not an argument for a lower chronology. Such an argument can only be advanced by diligently--in a pain-staking if not pain-loving fashion--sifting through the relevant data. But if such an empirical argument grounded in the data is advanced, and if we judge said argument to be a reasonable hypothesis, and if we find that as a consequence we can more readily build a narrative that more fully appreciates the simultaneously Jewish and Christian character of these texts and the persons responsible for their creation, then barring biases that distort our understanding we should in fact be quite happy to welcome the consequent advance in our knowledge.
N.B. No, the early Christians probably did not regularly describe themselves as "Christians" during that era. Certainly, if they did, that self-description seems to have registered little in our extant data (although one must be wary of the naive supposition that the term could not have been current prior to its first extant use, a supposition that fundamentally seems to confuse knowing with looking). But in any case, as I am not talking about their own self-definition but rather our retrospective understanding of their development, this is a matter which simply does not matter. The decision to refer heuristically to these persons as "Christians" is quite different from and in no way implies the judgment that they referred to themselves as such.