anno Domini

Anno Domini (525- ), or AD for short, is Latin for “in the year of the Lord”, It means that the number that goes with it is the number of years since the birth of Jesus Christ. For example, it is now 2006 AD. That means it is two thousand and six years since the birth of Christ. This is how the West has commonly numbered its years since the ninth century after Christ.

Years before Christ are marked “BC” for “Before Christ”. Years BC count backwards: 14 BC, for example, comes before 13 BC.

The year before 1 AD is 1 BC. There is no 0 AD or BC. This stuff was invented before anyone in the West knew about zero. (Some say that is not why, but I forget their reasoning.)

In English when a year is given by itself, as in “Columbus discovered America in 1492″, AD is understood.

AD and BC compared to other systems for numbering years:

01 Sep 5509 BC	anno mundi – Byzantine – creation of the world
07 Oct 3761 BC	anno mundi – Jewish – creation of the world
2016 BC	anno Abrahami – birth of Abraham
01 Jul 776 BC	Olympiads (periods of four years) – from the first Olympics
21 Apr 753 BC	AUC – the founding of Rome
Sep-Dec 312 BC	Seleucid – start of the empire
01 Jan 1 AD	anno Domini – Christian, Western – the birth of Christ
16 Jul 622 AD	AH – Muslim – from the Hegira

Or, as I prefer to put it, the sun will be at the star of Regulus on the first day of spring in about the year 16,892 AD.

Eusebius and Jerome used anno Abrahami. Josephus used the Seleucid years.

CE and BCE: AD and BC are plainly Christian names and not everyone likes that. Jews, for example, do not call Jesus “Lord”. So some use CE (Common Era) and BCE (Before the Common Era) instead. So 2006 AD becomes 2006 CE. Same years, different names.

CE and BCE seem to be mainly used by American scholars. Among common people the Common Era is an affected usage.

Of course, you can avoid AD or CE or whatever by just using + and -, or just -. Example: Aristotle was born in -384, as opposed to 384 BC or 384 BCE.

AD was invented in 525 AD by Dionysius Exiguus. AD was originally not meant as a way to name years, as in a history book. It was invented to make it easier to work out what day Easter falls on – the first Sunday after the first full moon of spring.

AD did not become a way to name years till the early 700s when Bede used it in his history of England. Bede was also the first to use BC. By 800, it had become the established usage in the West under the empire of Charlemagne.

So was Jesus born in 1 AD? No. Because he was born under King Herod, he could not have been born later than 4 BC when Herod died. Most likely he was born in 6 or 7 BC. But 1 AD was the best anyone knew when AD was invented. It is too late to change it now.

See also:

• Gregorian calendar
• Christ
• Muslim
• Easter
• The West