Periodization is the attempt to categorize Universal History or divide time into named blocks. The result is a descriptive abstraction that provides a useful handle on periods of time with relatively stable characteristics. However, determining the precise beginning and ending to any "period" is often a matter of debate.

Most disciplines that attempt to talk fruitfully about the past find it helpful to break up what has happened in various ways, and to give these smaller units names. The names are valuable to the extent that they aid analysis and description. Periodization from the sciences includes the geologic Cretaceous or Jurassic periods, while examples from human history include the Zhou Dynasty, the Baroque Period, and the Harlem Renaissance.

To the extent that history is continuous and ungeneralizable, all systems of periodization are more or less arbitrary. Yet without named periods, however clumsy or imprecise, past time would be nothing more than scattered events without a framework to help us understand them. Nations, cultures, families, and even individuals, each with their different remembered histories, are constantly engaged in imposing overlapping, often unsystematized, schemes of temporal periodization; periodizing labels are continually challenged and redefined. One historian may write a new history of the Renaissance in Europe; another may claim that there was no such thing as the European Renaissance.