When someone refers to a year as A.D., what is the starting point from which they are counting?

Establishing the date when an event occurred could be a challenge for those living in the ancient world. In many societies, dates were reckoned relative to the rule of a particular person. That person varied with where you lived. At the time of the Peloponnesian War, the Athenian writer, Thucydides, dated the events three ways: by the priestess of Hera at Argos, the archon of Athens, and the ephor of Sparta.

The lists of the archons of Athens were well established in the fifth century BC. A similar list of ephors was established in Sparta. Another list used for dating relied on the victors of the Olympic games, which were conducted every 4 years and drew participation from many Greek cities.

The games that were held in 776 BC were defined as the first, and each Olympiad lasted 4 years. The first year of the first Olympiad, ol. 1,1 equals 776 BC, so ol. 116,3 is 314 BC. The list of victors was recorded by the end of the 5th century BC, and Greek historians were using the Olympiad system for dates in their writings by the fourth century BC.

In Rome, years were labeled with the names of the two consuls that were elected each year. Lists of consuls (fasti) date back to 509 BC, although lists predating 300 BC may not be reliable.

There were several dating systems in popular use during the Republic and the Empire.

The most common was to date a year by the names of the two consuls of Rome. During the Empire, these men took office on January 1. Consular dating lasted through the Republic and into the Empire until AD 537, when Justinian introduced an official system of dating based on the year of an emperor’s reign. Some people continued to date by consuls until AD 611.

Another way of reckoning in the later Empire was based on the due date for delivery of taxation “in kind,” where taxes were paid with food and goods instead of coinage. The financial year started September 1. From AD 287 on, this taxation in kind was called the inductio (induction).

Yet another way of dating used as its reference point the founding of the city of Rome (ab urbe condita). Tradition holds that Rome was founded on April 21 in 753 BC.

The dating system used in the Hellenized parts of the eastern Empire was often based on the Greek practice of referring to the 4-year Olympiad cycle. Dates were expressed in a format such as the 3rd year of the 200th Olympiad (ol. 200,3)

In the Roman provinces, local dating systems were often used. These might be based on the year of a king’s rule, the time of service of a high priest, or a reference to a zero-point year of a key event in the people’s history.

Dating conventions are sometimes confusing. When someone refers to a year as A.D., what is the starting point from which they are counting? It depends on when they are living.

If the person was writing before our A.D. 535 (often called 535 CE), it was “after Diocletian” and counted from the reign of Diocletian (284-305), who is famous for aggressively persecuting Christians by imperial decree. Years in the Anno Diocletiani system have a starting point of August, 284 CE.

If it’s after 800 CE, it is Anno Domini and counted from the approximate birth year of Jesus Christ. This calendar has no zero, jumping from 1 B.C. (before Christ) to A.D. 1 (year of our Lord). The designators CE (common era) and BCE (before common era) have come into academic use to avoid reference to Jesus of Nazareth by using A.D. or AD and B.C. or BC.

If it’s between 535 and 800 CE, it could be either.

Sources:

Adkins, Lesley and Roy A. Adkins. Handbook to Life in Ancient Rome. New York: Oxford University Press, 1998.

Samuel, Alan E., “Calendars and Time-Telling.” Civilization of the Ancient Mediterranean: Greece and Rome. Ed. Michael Grand and Rachel Kitzinger, Vol. 1. New York: Charles Scribner’s Sons, 1988.

Art and Picture Collection, The New York Public Library. “View of the Capitol and Forum at the time of the emperors.” The New York Public Library Digital Collections. 1896. http://digitalcollections.nypl.org/items/510d47e4-600e-a3d9-e040-e00a18064a99