Postmodern is not a commonly used era in historical periodization. The three most commonly used eras are Ancient, Medieval, and Modern.

The Ancient era is generally considered to have begun with the rise of civilization in Mesopotamia around 3500 BCE.

The Medieval era is generally considered to have ended with the Renaissance in the 14th century.

The Modern era is generally considered to have begun with the Age of Exploration in the 15th century.

The American Revolution is not a major historical event that occurred during the Ancient era. It occurred during the Modern era.

The War of the Roses is not a major historical event that occurred during the Medieval era. It occurred during the Modern era.

The Cold War is not a major historical event that occurred during the Modern era. It occurred during the Contemporary era.

Historical periodization is the division of history into distinct periods of time.

The purpose of historical periodization is to make history easier to study, help historians understand the past, and identify patterns and trends in history.

Historical periodization is based on a variety of factors, including political events, economic events, social events, and cultural events.

The boundaries between historical periods are often both clearly defined and vague and overlapping.

Historical periodization is both a static and dynamic system. It is static in the sense that the boundaries between historical periods are fixed, but it is also dynamic in the sense that the interpretation of these periods can change over time.

Historical periodization is both a necessary and useful tool for historians. It is necessary because it allows historians to organize and understand the vast amount of information that is available about the past. It is also useful because it allows historians to identify patterns and trends in history.

Historical periodization is both a contested and uncontested concept. It is contested in the sense that there is no one universally agreed-upon way to divide history into periods. However, it is also uncontested in the sense that most historians agree that some form of periodization is necessary in order to study history.