The traditional date for the founding of Rome of 21 April 753 BC, was initiated by 1st century BC scholar
Marcus Terentius Varro. Varro may have used the consular list with its mistakes and called the year of the first consuls "245 ab urbe condita", accepting the 244-year interval from
Dionysius of Halicarnassus for the kings after the foundation of Rome. The correctness of Varro's calculation has not been confirmed, but it is still used worldwide.
Claudius (ruled 41–54) onwards, Varro's calculation superseded other contemporary calculations. Celebrating the anniversary of the city became part of imperial
propaganda. Claudius was the first to hold magnificent celebrations in honour of the city's anniversary, in 48
AD, 800 years after the founding of the city.
Antoninus Pius held similar celebrations, in 121 and 147/148 respectively.
Philip the Arab celebrated Rome's first
millennium, together with
Ludi saeculares for Rome's alleged tenth
Coins from his reign commemorate the celebrations. A coin by a contender for the imperial throne,
Pacatianus, explicitly states "Year one thousand and first", which is an indication that the citizens of the Empire had a sense of the beginning of a new era, a Saeculum Novum.
When the Roman Empire turned Christian in the 4th century, the imagery came to be used in a more
metaphysical sense, and removed legal impediments to the development and public use of the
Anno Domini dating system, which came into general use during the reign of