Authors’ Note: The B.C.E./C.E. Dating System

WHEN WERE YOU BORN? What year is it? We customarily answer questions like these with a number, such as “1991” or “2008.” Our replies are usually automatic, taking for granted the numerous assumptions Westerners make about how dates indicate chronology. But to what do numbers such as 1991 and 2008 actually refer? In this book the numbers used to specify dates follow a recent revision of the system most common in the Western secular world. This system reckons the dates of solar years by counting backward and forward from the traditional date of the birth of Jesus Christ, over two thousand years ago.

Using this method, numbers followed by the abbreviation B.C.E., standing for “before the common era” (or, as some would say, “before the Christian era”), indicate the number of years counting backward from the assumed date of the birth of Jesus Christ. B.C.E. therefore indicates the same chronology marked by the traditional abbreviation B.C. (“before Christ”). The larger the number preceding B.C.E. (or B.C.), the earlier in history is the year to which it refers. The date 431 B.C.E., for example, refers to a year 431 years before the birth of Jesus and therefore comes earlier in time than the dates 430 B.C.E., 429 B.C.E., and so on. The same calculation applies to numbering other time intervals calculated on the decimal system: those of ten years (a decade), of one hundred years (a century), and of one thousand years (a millennium). For example, the decade of the 440s B.C.E. (449 B.C.E. to 440 B.C.E.) is earlier than the decade of the 430s B.C.E. (439 B.C.E. to 430 B.C.E.). “Fifth century B.C.E.” refers to the fifth period of 100 years reckoning backward from the birth of Jesus and covers the years 500 B.C.E. to 401 B.C.E. It is earlier in history than the fourth century B.C.E. (400 B.C.E. to 301 B.C.E.), which followed the fifth century B.C.E. Because this system has no year “zero,” the first century B.C.E. covers the years 100 B.C.E. to 1 B.C.E. Dating millennia works similarly: the second millennium B.C.E. refers to the years 2000 B.C.E. to 1001 B.C.E., the third millennium to the years 3000 B.C.E. to 2001 B.C.E., and so on.

To indicate years counted forward from the traditional date of Jesus’s birth, numbers are followed by the abbreviation C.E., standing for “of the common era” (or “of the Christian era”). C.E. therefore indicates the same chronology marked by the traditional abbreviation A.D., which stands for the Latin phrase anno Domini (“in the year of the Lord”). A.D. properly comes before the date being marked. The date A.D. 1492, for example, translates as “in the year of the Lord 1492,” meaning 1492 years after the birth of Jesus. Under the B.C.E./C.E. system, this date would be written as 1492 C.E. For dating centuries, the term “first century C.E.” refers to the period from 1 C.E. to 100 C.E. (which is the same period as A.D. 1 to A.D. 100). For dates C.E, the smaller the number, the earlier the date in history. The fourth century C.E. (301 C.E. to 400 C.E.) comes before the fifth century C.E. (401 C.E. to 500 C.E.). The year 312 C.E. is a date in the early fourth century C.E., while 395 C.E. is a date late in the same century. When numbers are given without either B.C.E. or C.E., they are presumed to be dates C.E. For example, the term eighteenth century with no abbreviation accompanying it refers to the years 1701 C.E. to 1800 C.E.

No standard system of numbering years, such as B.C.E./C.E., existed in antiquity. Different people in different places identified years with varying names and numbers. Consequently, it was difficult to match up the years in any particular local system with those in a different system. Each city of ancient Greece, for example, had its own method for keeping track of the years. The ancient Greek historian Thucydides, therefore, faced a problem in presenting a chronology for the famous Peloponnesian War between Athens and Sparta, which began (by our reckoning) in 431 B.C.E. To try to explain to as many of his readers as possible the date the war had begun, he described its first year by three different local systems: “the year when Chrysis was in the forty-eighth year of her priesthood at Argos, and Aenesias was overseer at Sparta, and Pythodorus was magistrate at Athens.”

A Catholic monk named Dionysius, who lived in Rome in the sixth century C.E., invented the system of reckoning dates forward from the birth of Jesus. Calling himself Exiguus (Latin for “the little” or “the small”) as a mark of humility, he placed Jesus’s birth 754 years after the foundation of ancient Rome. Others then and now believe his date for Jesus’s birth was in fact several years too late. Many scholars today calculate that Jesus was born in what would be 4 B.C.E. according to Dionysius’s system, although a date a year or so earlier also seems possible.

Counting backward from the supposed date of Jesus’s birth to indicate dates earlier than that event represented a natural complement to reckoning forward for dates after it. The English historian and theologian Bede in the early eighth century was the first to use both forward and backward reckoning from the birth of Jesus in a historical work, and this system gradually gained wider acceptance because it provided a basis for standardizing the many local calendars used in the Western Christian world. Nevertheless, B.C. and A.D. were not used regularly until the end of the eighteenth century. B.C.E. and C.E. became common in the late twentieth century.

The system of numbering years from the birth of Jesus is far from the only one in use today. The Jewish calendar of years, for example, counts forward from the date given to the creation of the world, which would be calculated as 3761 B.C.E. under the B.C.E./C.E. system. Under this system, years are designated A.M., an abbreviation of the Latin anno mundi, “in the year of the world.” The Islamic calendar counts forward from the date of the Prophet Muhammad’s flight from Mecca, called the Hijra, in what is the year 622 C.E. The abbreviation A.H. (standing for the Latin phrase anno Hegirae, “in the year of the Hijra”) indicates dates calculated by this system. Anthropology commonly reckons distant dates as “before the present” (abbreviated B.P.).

History is often defined as the study of change over time; hence the importance of dates for the historian. But just as historians argue over which dates are most significant, they disagree over which dating system to follow. Their debate reveals perhaps the most enduring fact about history—its vitality.