centuries

Centuries are periods of 100 years used to group historical events. The term comes from the Latin centum, meaning hundred.

In the common era dating system, the 1st century spans 1 through 100 CE, the 2nd spans 101–200 CE, and so on. The 21st century covers 2001–2100 CE, since there is no year 0 in this system. Before 1 CE, centuries are counted in the same way for BCE: the 1st century BCE covers 100 BCE to 1 BCE, the 2nd century BCE covers 199 BCE to 100 BCE.

Centuries are a convenient framework for describing broad political, social, technological, and cultural changes, offering a balance between the detail of decades and the scope of longer periods. They are named by ordinal numbers (the 5th century, the 18th century) and are commonly used in historical writing, education, and reference works. In scholarly usage, centuries are often subdivided into decades or half-centuries to denote finer timing without resorting to year-by-year detail.

Because calendars and eras vary across cultures, the exact dating of events can differ outside the common era framework. Nevertheless, the century remains a standard unit in historiography for organizing and comparing long spans of history.