Consuls and Years

How did the Romans keep track of years?   Formally, they dated events ab urbe condita, from the founding of the city, which was traditionally 753 BC.  But in practical terms, people generally referred to the year by the two consuls for that year: "during the consulship of Scipio and Crassus", for example.  Roman magistrates were elected to one year terms, and although it was not unheard of for a man to be elected to the same post, it very seldom happened, so it was easy for people to refer to the year by the names of the consuls.  The closest modern analogy is probably when we refer to something that happened "during the Reagan administration", or on a personal level, "that was the year we got married". 

Consuls were the chief executives of the Roman Republic.  There were two of them because the Romans hated autocrats, and did not want absolute power in the hands of one man: history proved that they were right to do so. Many postitions in the Roman state (governors of provinces or commanders of armies, for example) were only filled by ex-consuls (or ex-praetors, who were one step below the consuls in the hierarchy of Roman magistrates).   Even during the Empire the consulships were still filled annually, because the bureaucracy of the Roman state required officials to run it.

This particular inscription can be dated to the year 291 AD because we have lists of all the consuls for each year of the Republic and the Empire from 509 BC up until the middle of the 6th century AD. http://en.wikipedia.org/wiki/List_of_Roman_Consuls