I agree that the timing of the incarnation involves 'καιρός, but I see no reason whatsoever to identify then current philosophy as a component of the auspiciousness of that era. 

We can easily identify, IMHO, four distinct philosophical world views through which revelations has migrated. (1) The Hebrew thought structures were, of course, the philosophical context of revelation conveyed to us by the OT and it was also the thought milieu of Jesus own pronouncement. (2) The seven early Greek councils that developed and defined core element of our faith re-expressed revelation in neoplatonic terms. (3) The great theological synthesis of the high middle ages translated and developed all of that into scholastic Aristotelian philosophical terms. (And the neoplatonic and Aristotelian world views are about as diametrically opposed to one another as any two philosophies can be!). (4) Finally, today, we are in the midst of perhaps the most dramatic transformation of theology as evolving.