Periodisation

Periodization is the process or study of categorizing the past into discrete, quantified named blocks of time in order to facilitate the study and analysis of history. This results in descriptive abstractions that provide convenient terms for periods of time with relatively stable characteristics. However, determining the precise beginning and ending to any "period" is often arbitrary. It has changed over time in history.

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, but once established, a period "brand" is so convenient that many are very hard to shake off.

The division of history into "ages" or periods is very old, and recorded practically as early as the first development of writing. The Sumerian King List operates with dynastic regnal eras. The classical division into a Golden Age, Silver Age, Bronze Age, Heroic Age and Iron Age goes back to Hesiod. One Biblical periodization scheme commonly used in the Middle Ages was Saint Paul's theological division of history into three ages: the first before the age of Moses (under nature); the second under Mosaic law (under law); the third in the age of Christ (under grace). But perhaps the most widely discussed periodization scheme of the Middle Ages was the Six Ages of the World, where every age was a thousand years counting from Adam to the present, with the present time (in the Middle Ages) being the sixth and final stage.

Not only do periodizing blocks inevitably overlap, they often seemingly conflict with or contradict one another. Some have a cultural usage ("the Gilded Age"), others refer to prominent historical events ("the Inter-War years: 1918–1939"), yet others are defined by decimal numbering systems ("the 1960s", "the 17th century"). Other periods are named from influential or talismanic individuals ("the Victorian Era", "the Edwardian Era", "the Napoleonic Era").

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