Please fight my ignorance. What exactly does BC and AD stand for, in the context of time? I will show my ignorance here and say that I thought BC stood for Before Christ, and AD stood for After Death (referring to Christ).
However, one time I read that AD stood for Anno Domini (sp?) or something like that. Could someone please clarify all of this for me in a short, understandable answer?
Thanks!
“Anno Domini” = “In the year of our Lord”
See Wiki for details.
AD does stand for Anno Domini, which is Latin for “In the Year of the Lord”. Around the year 500, this monk named Dionysis Exiguus decided there needed to be an accurate way of calculating dates, and he decided that dates should be calculated from the birth of Jesus. So, he figured out the date Jesus was born and called it AD 1 There’s a lot of evidence he got his calculations wrong, and that Jesus was really born sometime between 6-4 BC, but it’s what he calculated.
Well I guess I wasn’t so far off.
Thank you silenus!
I live to serve. 
You’ll occasionally run across BCE as well. It’s for Before Common Era, which is a way of referencing the same timeframe as BC without offending infidels.
The current trend, particularly in the sciences, is to replace AD and BC with CE (the Common Era) and BCE (Before the Common Era).
Of course, the problem with having BC stand for Before Christ and AD for After Death, is that it leaves about 33 years unaccounted for (the years between the birth and death of Christ).
Now it is becoming politically correct to use the terms CE and BCE (Common Era and Before Common Era) to avoid any reference to religion when referring to dates.
P.S. On preview, it looks like I need to type faster.
Thank you Captain! So, here is a stupid assumption/joke: nobody would know what year it was during the BC time right? Like a person couldn’t say it was 53 BC because he didn’t know that in 53 more years Jesus would arrive, right?
I am just wanting to clarify if I am understanding this correctly.
Absolutely. As mentioned above, the “BC” designation did not exist until centuries later.
Prior to the AD/BC designation, most people refered to dates by such things as “in the 7th year of the reign of King Oxymoron”.
Well, right, they wouldn’t say they lived in 53 BC or something. They had other calenders and other ways of dating years. For instance, in the Jewish calendar, today is the 27th day of Shevat in the year 5767. That’s because the Jewish calendar dates from the creation of the world, which, traditionally, Jews believe was 5767 years ago. One of the things the Romans did was to date things “A.U.C”, from the year Rome was founded. So you might see a date that said 500 A.U.C. They might also have used, “In the fifth year of the Emperor Nero”. or, “In the Year that Publius Flaccus and Marcellus Caecellus Metellus were Consuls”. (The Romans elected consuls for a one year period)
So, they knew what year it was. They just used a different dating system than the one you’re used to.
OK, now my head is starting to hurt. It seems it is more complicated than I thought.
HEY Q.E.D. waves
I once had a devout Christian for a roommate.
He preferred CE and BCE because as a detail freak, he hated being 1-5 years off due to that monk miscalculating the actual birthyear of Christ.
Did the Jews actually use this calendar in ancient times, or is it a fairly modern invention? I don’t think that this method of referring to years is ever referenced in the Old Testament.
Small nitpik on the idea that using CE and BCE are becoming “politically correct” and that it is a recent event to switch to that usuage-
I was taught CE and BCE over 30 years ago in Hebrew School, since it seemed odd to discuss history of the Jewish people, while in synagogue, using direct references to the centrality of Christianity in every day life.
So it’s not recent and not just “PC” but represents a fundemental way of viewing the world from a non-Christian point of view.
OK then, carry on.
Although AUC (Ad Urbe Condita, “since the building of the city,” referring to the legendary founding of Rome in 753 BC[E]) is the more famous, probably the most common calendar system in the ancient world (i.e., the last couple of centuries BC) was the Seleucid Era, which dated things from the accession of Alexander’s general Seleucus I to the throne of an area covering roughly the present Middle East, from Syria into most of Iran. We’re presently in 2319 SE.
Interesting detail: There Is No Year Zero.
So you go right from 1 B.C. to 1 A.D. (Or 1 B.C.E. to 1 C.E. for you infidel types). If you treat dates like our normal system of numbers you can get an error of one year if your span covers the period assigned to the Birth of Christ, unless you’re careful.
And don’t get started on when Christ was really born and how to reconcile the various historical events and the gospels. I don’t want to open that can of worms.
Ab is the preposition you want. Ad would be “to the building of the city”, which would be either anachronistic or suggestive of unusual prescience. 
I was taught that the Greeks started their calendar from 776 BC, the first Olympics.
Please allow me to toss in the notion of Julian Date, which was created in the 1500’s to try to avoid all the issues with before and after some arbitrary point in history. It was designed for astronomical usage so that the time between events could be calculated directly without having to cross the border of before and after.
For details of this interesting invention, check this Wikipedia article or Google for other treatments.