This resource explores the concept of chronology, which is the order of events in history. It emphasizes the importance of organizing time for better understanding, akin to chapters in a book. The text discusses how historians group events into eras—distinct periods characterized by significant changes such as inventions, wars, or cultural shifts. Additionally, it introduces the historical number line, outlining the concept of 'no year zero' between BCE (Before Common Era) and CE (Common Era). Different terms for marking time (BC/AD and BCE/CE) are examined to highlight how they both indicate the same historical periods. The resource includes examples of key dates in Roman history, discussions on how time marking affects perceptions of events, and emphasizes the importance of consistency in historical research.