What is "ab urbe condita"

prep.phr. From the founding of the city (i.e. Rome, traditionally dated to 753 BC): used by some Ancient Roman historians to identify particular Roman years.

"ab urbe condita" (related to "anno urbis conditae"; A. U. C., AUC, a.u.c.; also "anno urbis", short a.u.) is a Latin phrase meaning "from the founding of the City (Rome)", traditionally dated to 753 BC. AUC is a year-numbering system used by some ancient Roman historians to identify particular Roman years. Renaissance editors sometimes added AUC to Roman manuscripts they published, giving the false impression that the Romans usually numbered their years using the AUC system. The dominant method of identifying Roman years in Roman times was to name the two consuls who held office that year. The regnal year of the emperor was also used to identify years, especially in the Byzantine Empire after 537 when Justinian required its use.