It was rarely used in the Roman calendar and in the early Julian calendar – naming the two consuls that held office in a particular year was dominant.AD 2019 is thus approximately the same as AUC 2772 (2019 753).A calendar era is the year numbering system used by a calendar.
Soon afterwards, imperial regnal dating was adopted in its place.
Another method of dating, rarely used, was anno urbis conditae (Latin: "in the year of the founded city" (abbreviated AUC), where "city" meant Rome).
Each year at the Akitu festival (celebrating the Mesopotamian new year), one of a small group of high officials (including the king in later periods) would be chosen by lot to serve as the limmu for the year, which meant that he would preside over the Akitu festival and the year would bear his name.
The earliest attested limmu eponyms are from the Assyrian trading colony at Karum Kanesh in Anatolia, dating to the very beginning of the 2nd millennium BC, and they continued in use until the end of the Neo-Assyrian Period, ca. Assyrian scribes compiled limmu lists, including an unbroken sequence of almost 250 eponyms from the early 1st millennium BC.
In East Asia, reckoning by era names chosen by ruling monarchs ceased in the 20th century except for Japan, where they are still used.
For over a thousand years, ancient Assyria used a system of eponyms to identify each year.
Another system that is less commonly found than might be thought was the use of the regnal year of the Roman emperor.
At first, Augustus indicated the year of his reign by counting how many times he had held the office of consul, and how many times the Roman Senate had granted him Tribunican powers, carefully observing the fiction that his powers came from these offices granted to him, rather than from his own person or the many legions under his control.
(It is often incorrectly given that AUC stands for ab urbe condita, which is the title of Titus Livius's history of Rome.) Several epochs were in use by Roman historians.
Modern historians usually adopt the epoch of Varro, which we place in 753 BC.
The Olympic Games provided the various independent city-states with a mutually recognizable system of dates. Another common system was the indiction cycle (15 indictions made up an agricultural tax cycle in Roman Egypt, an indiction being a year in duration).