Reckoning time is central to all historical study, for history is essentially the story of change over time. Recently it has become standard in the Western world to refer to dates prior to the birth of Christ as B.C.E. (before the Common Era), replacing the earlier B.C. (before Christ) usage. This convention is an effort to become less Christian-centered and Eurocentric in our use of language, although the chronology remains linked to the birth of Jesus. Similarly, the time following the birth of Christ is referred to as C.E. (the Common Era) rather than A.D. (Anno Domini, Latin for “year of the Lord”). Dates in the more distant past are designated in this book as BP (“before the present,” by which scholars mean 1950, the dawn of the nuclear age) or simply as so many “years ago.” Of course, these conventions are only some of the many ways that human societies have charted time, and they reflect the global dominance of Europeans in recent centuries. But the Chinese frequently dated important events in terms of the reign of particular emperors, while Muslims created a new calendar beginning with Year 1, marking Muhammad’s forced relocation from Mecca to Medina in 622 C.E. As with so much else, the maps of time that we construct reflect the cultures in which we have been born and the historical experience of our societies.

World history frequently deals with very long periods of time, often encompassing many millennia or centuries in a single paragraph or even in a single sentence. Such quick summaries may sometimes seem to flatten the texture of historical experience, minimizing the immense complexities and variations of human life and dismissing the rich and distinctive flavor of individual lives. Yet this very drawback of world history permits its greatest contribution to our understanding—perspective, context, a big picture framework in which we can situate the particular events, societies, and individual experiences that constitute the historical record. Such a panoramic outlook on the past allows us to discern patterns and trends that may be invisible from the viewpoint of a local community or a single nation. In the narrative that follows, there will be plenty of particulars—events, places, people—but always embedded in some larger setting that enriches their significance.