The document discusses different systems for measuring and representing time in history. It explains common dating conventions like BC, AD, BCE and CE and eras like prehistoric, ancient, medieval and modern. The document also outlines how events are chronologically organized using timelines to help understand history from the beginning to the present. Key features of timelines mentioned include using consistent scales, dates, descriptions and visuals to sequentially illustrate important events over periods of time from an individual's life or the entire world history.