By Henry C K Liu
"In chronology, an era is a period reckoned from an artificially fixed point in time, as before or after the birth of Christ: BC for Before Christ and AD for Anno Domini (year of the Lord). There are less known but also significant points in historical time beside the birth of Christ. The alleged creation of the world in Jewish mythical history is equivalent to 3761 BC, and in Byzantine history, the creation date was 5508 BC. The founding of the city of Rome took place in 753 BC, with subsequent years marked AUD for ad urbe condita (from the founding of the city). The hijira marks the migration of the Prophet Mohammed to Medina from Mecca in AD 622. Abbreviated AH, it is the starting timepost for all Muslims. "
"Periodization, a complex problem in history, is the attempt to categorize or divide historical time, mentality or events into discrete named blocks. History is in fact continuous, and so all systems of periodization are to some extent arbitrary. History does not end as long as the human species survives. Those who proclaim the end of history are predicting the death of civilization, not the victory of neo-liberalism as heaven on Earth."
"It is nevertheless useful to segment history so that the past can provide lessons to the present by being conceptually organized and significant changes over time articulated. Different peoples and cultures have different histories, and so will need different models of periodization. Periodizing labels constantly change and are subject to redefinition as contemporary perceptions change. A historian may claim that there is no such thing as modernity, or the Enlightenment or the Renaissance, or the Nuclear Age, while others will defend the concept."
Although Liu obviously nurses a particular political bias, I found this article interesting. Although it is not purely about the Roman Empire, there is an extensive discussion of this authori's viewpoint of what constituted the formation of the Holy Roman Empire and the political environment surrounding that formation.