In historiography, periodization is the process or study of categorizing the past into discrete, quantified, and named blocks of time for the purpose of study or analysis. This is usually done in order to understand current and historical processes, and the causality that might have linked those events.
Petrarch conceived of the idea of a European "Dark Age" which later evolved into the tripartite periodization of Western history into Ancient, Post-classical and Modern.
The Ages of Man are the historical stages of human existence according to Greek mythology and its subsequent Roman interpretation.
Lucas Cranach the Elder, The Golden Age
Lucas Cranach the Elder, The Golden Age (2nd version)
Lucas Cranach the Elder, The Silver Age
Virgil Solis, The Iron Age