They don’t appear often in day-to-day doings, but the initials used with dates are there for a good reason. The A.D., B.C. and C.E. that are placed with a year are an indication of time and history. Each is rooted in the Latin language. Understanding what is behind the B.C. and A.D. markings is a small but important bit of information that can help you have a deeper knowledge of history and events.


A.D., B.C. and C.E. are put in place with a year to distinguish it as being before the birth of Christ or after.

Basics of the Gregorian Calendar

The Gregorian calendar is the most widely used and accepted calendar in the world today. Named after Pope Gregory XIII, the Gregorian calendar is a solar calendar based on a common year divided into 12 months of irregular lengths and 365 days. The second month, February, is made up of 28 days, while the remaining 11 months have either 30 or 31 days. Every four years there is a leap year, when one extra day, called an intercalary, is added. This extra day helps to keep the calendar in balance throughout the changing seasons as the years accumulate. It keeps astronomical events such as equinoxes and solstices in alignment with the days of the year.

Definition of A.D.

A.D. is the abbreviation for anno Domini. It stems from medieval Latin. It means “in the year of our Lord.” The international standard is to count years based on the general agreement of when Jesus was born.

The anno Domini meaning evolved in the early Middle Ages from a need to know when Easter fell within the calendar year. In what was known as Easter tables, mathematicians kept calculations to have Easter fall on the Sunday that followed the full moon that came directly after the spring equinox in March. In A.D. 525, the monk Dionysius Exiguous of Scythia Minor counted the years since what was accepted as the year of Christ’s birth and entered that as a date to further help future monks quickly pinpoint when Easter would be celebrated by the masses.

Beginnings of B.C.

More than 200 years after Dionysius put a system in place to mark the passing of years, the idea of B.C. came into play. In the year 731, the Venerable Bede of North Umbria published a paper that brought attention to the need for counting the years before Christ’s birth. Bede’s work made Dionysius’s system even more widely used and introduced the use of B.C. If an event happened prior to A.D. 1, it was labeled B.C. Unfortunately, Bede started B.C. year one the year before A.D. year one, so there is no year zero. By the 15th century, the entire world was using the A.D./B.C. system.

Consider C.E. and B.C.E.

An alternative form of A.D. and B.C. has formed rather recently. The term C.E. has carved a place among modernists. It means “common era.” There is also “B.C.E.,” which stands for “before common era.” It was first used in a book by Johannes Kepler that was published in 1615. It has been used in the late part of the 20th century in academic and scientific publications and by writers and publishers who preferred to underscore a leaning toward secularism.

Understanding Century Distinctions

The first century A.D. was the year 1 through 99. This means the second century began in the year 100 A.D. This can be confusing when attempting to figure out which century we’re in or what century a specific date is in. For instance, the year 1650 was smack dab in the middle of the 17th century. A century is 100 years. When the year rolls over from 99 to 00, it starts a new century.

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