When reading about history, we often encounter the abbreviations “B.C.” and “A.D.” or “B.C.E.” and “C.E.” to denote time periods. So where do these terms come from, and what do they mean?
These are terms that mark the time before and after the birth of Jesus Christ. Sometimes they are also written as “C.E.” and “B.C.E.”
What is A.D.?
The astronomical clock at the Cathedral of Messina, Sicily, Italy (Photo: Eye Ubiquitous/ Getty Images).
“A.D.” stands for “anno domini”, which in Latin means “in the year of our Lord,” specifically referring to the time when Jesus Christ was born. “B.C.” stands for “before Christ.”
In historical texts, the system for marking years is based on a folk conception of the time of Jesus’s birth. Writing “A.D.” means the years after the birth of Christ, and “B.C.” refers to the years before that date.
In recent years, an alternative notation for B.C. and A.D. has emerged. Many documents use the abbreviations “C.E.” (Common Era) and “B.C.E.” (before Common Era) to avoid religious connotations.
In Vietnamese, these terms are commonly abbreviated as “CN” and “TCN”.
Before discussing the reasons behind and the origins of this abbreviation system, let’s explore some historical contexts.
The First Ecumenical Council aimed to standardize the date of Easter, leading to the establishment of the A.D. dating system. (Photo: Getty Images).
When was “A.D.” invented?
In the early Middle Ages in Europe, one of the most important calculations and a key motivation for conducting mathematical research was determining when to celebrate Easter.
In 325 A.D., the First Ecumenical Council decided that Easter would fall on the Sunday after the first full moon following the vernal equinox. The term “Computus” in Latin means “calculation,” which refers to the process of determining this important date, recorded in documents as the “Easter Table.”
In 525 A.D., one of those Easter Tables was modified by a monk named Dionysius Exiguus from Scythia Minor, who added a count of years from the birth of Christ, thus establishing the A.D. system.
Dionysius did not clarify how he determined the birth date of Jesus, but he likely used surviving texts from early Christians, such as those by Clement of Alexandria or Eusebius of Caesarea, to calculate the birth date.
Dionysius designated the year 1 A.D. as the year of Christ’s birth, but he may have miscalculated by a few years, as modern estimates suggest Jesus was born around 4 B.C. to 6 A.D.
What dating system was used before “A.D.”?
Dionysius developed this system to replace the Diocletian system, named after the Roman Emperor Diocletian (who reigned from 284 A.D. to 305 A.D.). The monk aimed to avoid recalling Emperor Diocletian, who enacted changes leading to the persecution and imprisonment of many Christians, as well as the burning of their churches and scriptures.
Two centuries after Dionysius devised the “A.D.” and “B.C.” notations were added to this system.
In 731, the Venerable Bede in the Kingdom of Northumbria published his book titled “Ecclesiastical History of the English People,” which expanded the year-marking system to include years prior to 1 A.D.
Years before 1 were numbered in a countdown when referring to events occurring before Christ or “before Christ” and abbreviated as “B.C.,” commonly written as “TCN” in Vietnamese.
The Venerable Bede was the first to use “B.C.” to count the years before the birth of Jesus Christ (Photo: Getty Images).
Why is there no year 0?
In the updated system of St. Bede, there is no year 0 because the concept of “zero” did not exist in Western Europe. Professor Charles Seife, Director of the Arthur L. Carter Journalism Institute at New York University, states: “St. Bede did not know of zero, and to him, the year before 1 A.D. was the year 1 B.C. There was no year 0. To him, zero did not exist.”
However, zero did exist in other places. The concept of zero first appeared in a document published in 628 A.D. by the Indian scholar Brahmagupta, although earlier cultures, including Babylonian and Maya cultures, also had concepts of zero.
It wasn’t until the 11th to 13th centuries that this concept became widely accepted in medieval Christian Europe.
When did A.D. and B.C. become popular?
The A.D. / B.C. system gained more usage from the 9th century, after the Holy Roman Emperor Charlemagne adopted it for marking the dates of state activities throughout Europe.
By the 15th century, all of Western Europe had adopted the A.D./B.C. system. The Gregorian calendar, introduced in the 16th century, also used this system, and since 1998, when the International Organization for Standardization (ISO) issued ISO 8601 detailing how to represent dates and times, this system has become an internationally accepted standard.
Holy Roman Emperor Charlemagne mandated the use of the A.D. / B.C. system in the 9th century (Photo: Getty Images).
How do B.C. and B.C.E. differ?
Some organizations and individuals have shifted to using the terms “B.C.E.” (Before Common Era) and “C.E.” (Common Era) instead of B.C. and A.D. to avoid sensitivity towards non-Christians and because B.C. and A.D. are considered inaccurate regarding the timeline of Jesus’s birth.
The terms C.E. and B.C.E. first appeared in 1795 in a book on astronomy and were used interchangeably with the term “Vulgar Era.” At that time, “vulgar” meant “common” rather than “vulgar.”
The term “Vulgar Era” was even used earlier in a book by the famous astronomer Johannes Kepler, who lived during the Holy Roman Empire.
