Decisive years, like decisive battles, are a favorite with historians. Some - like 1492 or 1776 or1941 - are obvious: Even people alive at those times knew that something big was up. More often, though, the great tidal waves of history begin as mere ripples, and only much later, looking back, is it possible to pin down the beginnings of an epochal shift. Such a time is the year one. Here, in this Quick Read, is its momentous story.