Question: “What do the letters B.C., A.D., BCE, and CE mean?”
Answer: All four of these oft-encountered terms are related to Jesus Christ.
B.C. and A.D. B.C. is short for “Before Christ”. While some people believe “A.D.” stands for “After Death”, “AD” or “A.D.” is actually from the Latin term, “anno Domini”, which means “in the year of the Lord”. It is supposed to refer to years counted from Christ’s birth. However, because of some inaccurate counting and some uncertainty over when Christ was born, there is probably a 4 to 8 year discrepancy with Christ probably being born between 8 B.C. and 4 B.C..
The B.C./A.D. calendar system was not established until around 500 A.D., well after the books of the Bible were written. See the citation from the Encyclopaedia Britannica below. So any references to B.C. or A.D. you read “in the Bible” are related to footnotes, commentaries, or other study aids supplied by the translators. While the original authors were miraculously inspired by God, translators are not. So we need to exercise some degree of caution when we use such aids.
BCE and CE. CE stands for “Common Era” or “Current Era” (although references to “Christian Era” can be found). BCE is “Before Common Era” or “Before Current Era”. CE and BCE dates are identical with A.D. and B.C. dates (for example, 2000 CE is the same as 2000 A.D.). This is a thinly veiled attempt by atheists and religious people other than Christians to remove Christian religious references from our culture.
From Encyclopaedia Britannica for “chronology: Christian”
The Christian Era is the era now in general use throughout the world. Its epoch, or commencement, is January 1, 754 AUC (ab urbe condita--"from the foundation of the city [of Rome]"--or anno urbis conditae--"in the year of the foundation of the city"). Christ's birth was at first believed to have occurred on the December 25 immediately preceding. Years are reckoned as before or after the Nativity, those before being denoted BC (before Christ) and those after by AD (anno Domini, "in the year of the Lord"). Chronologers admit no year zero between 1 BC and AD 1. The precise date of commencing the annual cycle was widely disputed almost until modern times, December 25, January 1, March 25, and Easter day each being favoured in different parts of Europe at different periods.
The Christian Era was invented by Dionysius Exiguus (c. AD 500-after 525), a monk of Scythian birth resident in Italy; it was a by-product of the dispute that had long vexed the churches as to the correct method of calculating Easter. Many churches, including those in close contact with Rome, followed 95-year tables evolved by Theophilus, bishop of Alexandria, and by his successor, St. Cyril; but some Western churches followed other systems, notably a 532-year cycle prepared for Pope Hilarius (461-468) by Victorius of Aquitaine. In 525, at the request of Pope St. John I, Dionysius Exiguus prepared a modified Alexandrian computation based on Victorius' cycle. He discarded the Alexandrian era of Diocletian, reckoned from AD 284, on the ground that he "did not wish to perpetuate the name of the Great Persecutor, but rather to number the years from the Incarnation of Our Lord Jesus Christ."
Somehow Dionysius reckoned the birth of Christ to have occurred in 753 AUC; but the Gospels state that Christ was born under Herod the Great--i.e., at the latest in 750 AUC. Dionysius' dating was questioned by the English saint Bede in the 8th century and rejected outright by the German monk Regino of Prüm at the end of the 9th. Nevertheless, it has continued in use to the present day, and, as a result, the Nativity is reckoned to have taken place before the start of the Christian Era.