As in any historical endeavor, periodization is an attempt to manage change, and present it coherently, by noting points where key breaks in framework occur. In world history, periodization has come to convey, particularly, shifts in the pattern of interactions and contacts among many, though not always all, major societies. In this article, the author contends for the current conventions about the long 19th century and the contemporary era. The idea of the 19th and 20th centuries as periods is deeply ensconced, and while it partly reflects a modern and substantively irrelevant fascination with centuries, it does have some merits beyond convention. Historians' definitions of periods, correspondingly, change only slowly--as witness the amazing number of social history projects that developed imaginative new topics while using the most conventional, often inappropriate periodization. Changing the early modern, long 19th, and contemporary divisions and definitions would involve lots of rethinking, and some conceptual courage. Textbooks would have to shift, committees like Advanced Placement would have to ruminate; individual teachers would have to figure out how comfortable they are with some modest retooling. Fortunately, the resulting recasting would hardly involve destruction of the entire old lecture notes. It would, however, shake things up a bit in some fruitful directions. At this juncture, the main point is to urge that a new debate be opened. Teachers know they have to get rid of 20th century, regardless: their students are now firmly in the 21st, and unless they are content with a really undesirable amount of choppiness that would have a brand new period open in the 1990s, they have to relabel a bit, at the very least. The author believes that the opportunity exists to do rather more, to use world history, and globalization, to provide the same breath of analytical fresh air that has been applied so successfully, by world historians, to earlier eras like the postclassical. (Contains 7 notes.)