Dating The Timeline In Ancient History

In ancient Greece and Rome, the different events of the past were not dated by individual years, but by the reigns of world leaders, set in a chronological order. For example, an ancient Athenian would likely have said that the Peloponnesian War began during the tenure of the archon, Pythodorus. Similarly, ancient Romans would probably date the death of Augustus’ able admiral, Agrippa, to the consulship of Valerius and Publius Sulpicius. Thankfully, some of these leaders had set periods of rule, or calculable events such as solar eclipses, during their reign. As a result, modern scholars can date the start of the Peloponnesian War to around 431BCE/BC and the death of Agrippa to 12 BCE/BC.

The use of reigns for dating, instead of a list of years, does not mean that the ancients had no concept of seasons and months—in fact, the months used in the modern Western world are descended from ancient Rome. Yet, calendars often varied from region to region; for example, over 300 different month names were used in ancient Greece. Furthermore, the regions did not agree on when the New Year began and put their selection of months in different orders. As a result, it was simply easier for ancient historians to date their topics by the reigns in which the events occurred.

Yet, some historians from the distant past did want to make their system of dating more precise. The Athenian historian, Thucydides, was probably the first to do this, and it took some creativity on his part to make his ambition come true. To increase the accuracy of the dating that he included in his History of the Peloponnesian War, Thucydides divided his timeline of the war into solar years, and narrowed it further by dividing the solar years into summer and winter seasons. As a result, he could write that a certain event occurred in the summer of the third solar year after the start of the Peloponnesian War.

Thankfully for modern readers from the West, Dionysius Exiguus (c. 470-544 CE/AD) and Bede (673-735 CE/AD) standardized and simplified the yearly timeline by scaling the dating of years from the approximate time of Jesus’ birth. Due to Bede, especially, the use of “A.D.” and “B.C.”, or more recently, “CE” and “BCE” has become the common method in the West for dating historical events.

Written by C. Keith Hansely.

Top picture attribution: (The Acropolis at Athens, by Leo von Klenze (1784–1864), [Public Domain] via Creative Commons).


  • History of the Peloponnesian War by Thucydides, translated by Rex Warner and introduced by M. I. Finley. New York: Penguin Classics, 1972.
  • The Roman History by Cassius Dio, translated by Ian Scott-Kilvert. New York: Penguin Classics, 1987.

Leave a Reply