What Do BC, AD, BCE, and CE Mean?
BC means Before Christ. AD is short for the Latin Anno Domini, meaning “in the year of the Lord.” BCE means Before Common Era, and CE means Common Era.
The first thing to understand is that we’re not talking about two different calendars. BC and BCE refer to the same years, and AD and CE refer to the same years. Julius Caesar was assassinated in 44 BC or 44 BCE. Jerusalem was destroyed by the Romans in AD 70 or 70 CE. The date hasn’t changed. Only the label has.
But that raises an interesting question. Why are we numbering the years this way in the first place?
Julius Caesar certainly didn’t think he was assassinated in 44 BC. Nobody walked around ancient Rome saying, “It’s 44 years before Christ.” And the first Christians didn’t wake up on January 1, AD 100 and celebrate the beginning of a new century.
Those numbers were assigned much later.
How Did People Date Years Before BC and AD?
There wasn’t a universal Year 1 in the ancient world.
Different civilizations had different ways of identifying years. Greeks sometimes dated events according to Olympiads or public officials. Romans commonly identified a year by the consuls who held office. Another Roman system counted from the traditional founding of Rome.
Jewish people had their own calendar and religious festivals.
That makes sense when you think about it. Before you can call something “Year 1,” you have to answer another question:
Year 1 from what?
Every system for numbering years needs a starting point.
One major development came with Julius Caesar. The Roman calendar had gotten badly out of alignment with the seasons, so Caesar instituted a reform in the first century BC. The resulting Julian calendar had 365 days in an ordinary year with an additional day every fourth year.
It worked remarkably well and remained dominant throughout much of Europe for more than 1,600 years.
But there’s an important distinction here. Julius Caesar helped establish the structure of the calendar. He didn’t create the BC/AD numbering system.
That came centuries later.
Where Did AD Come From?
By the sixth century, Christians were still using several ways of identifying years. One system counted years from the reign of the Roman emperor Diocletian.
There was something rather awkward about Christians numbering their years according to Diocletian. He was remembered for one of the Roman Empire’s most severe persecutions of Christians.
Around AD 525, a monk named Dionysius Exiguus was working on calculations involving the date of Easter. Instead of continuing to use the era associated with Diocletian, Dionysius developed a chronology centered on Jesus Christ.
He called the years Anno Domini nostri Jesu Christi—“the year of our Lord Jesus Christ.”
That’s where AD, Anno Domini, comes from.
And it clears up a common misconception. AD doesn’t mean “After Death.”
If it did, we’d have another problem. What would we call the roughly thirty years between the birth and death of Jesus?
Traditionally, AD is placed before the year:
AD 325
That’s because you’re essentially saying, “In the year of our Lord 325.”
BC normally follows it:
325 BC
In modern usage, BCE and CE generally follow the number:
325 BCE
325 CE
Was Jesus Really Born in AD 1?
Probably not.
There’s a strange little historical irony in our calendar: Jesus was probably born several years “before Christ.”
Historians commonly place his birth somewhere around 6–4 BC. Dionysius was working centuries after the events and apparently didn’t calculate the date exactly.
That doesn’t mean the whole calendar needs to be renumbered.
Once a dating system becomes established, its numbers become conventions. If historians discover that the original calculation was off by a few years, changing every historical date would create far more confusion than leaving the established system alone.
So saying that Jesus was born around 6–4 BC sounds contradictory, but it really isn’t. It simply means Jesus was probably born several years before the point that was later designated as the beginning of the Christian era.
Where Did BC Come From?
Dionysius was primarily concerned with numbering years forward from the Christian era. The systematic numbering of years before that point developed later.
The English monk and historian Bede played an important role in popularizing Christ-centered chronology. In the eighth century, he used dating corresponding to years “before the incarnation of the Lord.”
Eventually the familiar designation **BC—Before Christ—**became standard.
That gave us a timeline that looks like this:
3 BC → 2 BC → 1 BC → AD 1 → AD 2 → AD 3
Notice anything missing?
Why Isn’t There a Year Zero?
There isn’t one.
In traditional BC/AD chronology, 1 BC is immediately followed by AD 1.
The same is true if we use BCE and CE:
3 BCE → 2 BCE → 1 BCE → 1 CE → 2 CE → 3 CE
That’s because the system was created before Europeans routinely used zero as a number in the way we do today.
It can make calculations across the BC/AD boundary a little confusing. It also explains why the first century consisted of years 1 through 100 rather than 0 through 99.
Astronomers sometimes use a year zero because it makes mathematical calculations easier, but that’s a different numbering convention from traditional historical chronology.
What About the Gregorian Calendar?
The Julian calendar was remarkably good, but it wasn’t perfect.
Its year was slightly longer than the actual solar year. The difference was only a matter of minutes each year, which doesn’t sound like much. Give those minutes more than a thousand years to accumulate, though, and eventually you’ve got a problem.
By the sixteenth century, the calendar had drifted noticeably from the solar year, creating particular difficulties in calculating the date of Easter.
In 1582, Pope Gregory XIII introduced a reform. The leap-year rules were adjusted and the accumulated drift was corrected. The resulting Gregorian calendar eventually became the dominant civil calendar used internationally.
But here’s another distinction that’s easy to miss:
The calendar and the way we label its years aren’t the same thing.
The Gregorian calendar tells us how months, days, leap years, and years themselves are organized.
BC/AD and BCE/CE tell us how those years are numbered and labeled.
Where Did BCE and CE Come From?
This is where the subject sometimes becomes unnecessarily political.
It’s easy to assume that BCE and CE were invented recently as part of an effort to remove Jesus from the calendar. The history is more complicated than that.
Expressions equivalent to Common Era have existed for centuries. English use of “Common Era” goes back at least to the seventeenth century, with related terminology appearing in subsequent historical writing. Older writers even used expressions such as “Vulgar Era,” when vulgar could simply mean common or ordinary.
Today:
BCE = Before Common Era
CE = Common Era
The terminology became particularly useful in academic and interreligious settings.
A Jewish historian doesn’t necessarily want to describe a Roman event as happening “in the year of our Lord.” A secular archaeologist may not believe Jesus is Lord at all. BCE and CE allow people with very different religious beliefs to use the same chronology without making a theological statement.
Did BCE and CE Remove Jesus from the Calendar?
They removed the explicitly Christian words, but they didn’t change the numbers.
Jerusalem was destroyed in:
AD 70
or:
70 CE
Same year.
Alexander the Great died in:
323 BC
or:
323 BCE
Again, same year.
So there is a certain historical irony here. You can remove “Christ” and “Lord” from the terminology, but the dividing point remains where it was because the chronology itself developed from a Christian attempt to organize history around Jesus Christ.
Changing the labels doesn’t change their history.
Why Does Most of the World Use This Calendar?
Not because most of the world became Christian.
The explanation is primarily historical.
European societies used Christian chronology for centuries. As European influence spread through exploration, colonization, commerce, diplomacy, science, and international institutions, European methods of dating spread with it.
Eventually the Gregorian calendar became an international civil standard.
That doesn’t prevent other cultures and religions from maintaining their own calendars. Judaism still uses the Hebrew calendar. Islam uses the Hijri calendar. Other religious and cultural traditions have their own systems as well.
A Muslim businessman can therefore write 2026 on a contract without making a confession of Christian faith. He’s using an internationally standardized dating convention.
Should Christians Use BC and AD or BCE and CE?
I don’t think we need to turn this into another theological test.
I generally prefer BC and AD in Christian writing because they preserve the history and meaning of the system. Anno Domini—“in the year of the Lord”—is a reminder that this chronology was deliberately organized around Christ.
But I wouldn’t conclude that a Christian who writes BCE or CE is somehow denying Jesus.
They’re different labels for the same years.
In academic writing, archaeology, museums, or discussions involving people from different religious traditions, BCE and CE may be perfectly reasonable choices. Context matters.
What I wouldn’t do is pretend that BCE and CE represent a completely different, religiously neutral chronology that has nothing historically to do with Christianity. They don’t. The terminology is religiously neutral; the history of the numbering system isn’t.
A Calendar Tells a Story
We don’t normally think of a calendar as saying anything. It’s just numbers on a wall—or these days, numbers on a phone.
But calendars have histories.
Someone had to decide where the year begins. Someone had to determine how long a year is. Someone had to choose the reference point from which those years would be counted.
Romans could organize time around their consuls or the traditional founding of Rome. Jewish communities organized their calendar around their own sacred history and festivals. Christians eventually developed a chronology centered on Christ. Modern civilization inherited and standardized much of that system.
That’s how we ended up with four little abbreviations:
BC — Before Christ
AD — Anno Domini, “in the year of the Lord”
BCE — Before Common Era
CE — Common Era
Different labels. Same years.
And nearly two thousand years of history behind the deceptively simple question:
What year is it?