 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 name periods, however clumsy or imprecise, past time would be nothing more than scattered events without a framework to help us understand them. Modern 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, the 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 regleras. 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 St. 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 autumn to the present, with the present time in the Middle Ages being the sixth and final stage.