How did they know???

I regularly caused consternation among the nuns at my Catholic grade school.  During one religion class, we were being taught what "AD" and "BC" meant for calendar dates.  I raised my hand and asked how the people back then knew what to call it.  The teacher reiterated, "it's After Death and Before Christ, Jeffrey.  Now moving on..."  And I said:  no, no, back in 100 BC, how did they know to count the years backwards?  Did they know Christ was going to show up in 100 years??

The class erupted, of course.  This was a head-scratcher.  Nobody really had the presence of mind to tell me that they probably called the years something else back then.  I guess it's hard to see out of such an ingrained way of looking at things.

And now I have my answer:  over at The Renaissance Mathematicus, thonyc tells us that the use of "AD" started around the year 525, and "BC" came into use in the 1600s.  Apparently beforehand, they had numbered the years by the reigns of the popes.

And that's your history lesson for the day.


  1. One should note that we Jews still use an ancient Lunar calendar (this is the year 5771, but in a couple of days it will be 5772). Roman Orthodox and some other religions follow the Julian Calendar created by Julius Caesar in about 45(BC) instead of the one established by Pope Gregory (the Gregorian Calendar used by most of the world today). During Roman Times many of the years were set by the Emperor's reign, so it may be the 2nd of December in the 15th year of the Emperor. If you were discussing a previous period you'd have to name the Emperor who reigned then and what year in his reign you were talking about. That could get pretty confusing when really trying to pin down an historical event. People regularly lived to be in their 80's so they had quite a litany of dates to remember.

    Happy 5772 to you!

  2. I like David Foster Wallace's idea of selling naming rights to years just like baseball stadiums:
    Year of the Whopper
    Year of the Tucks Medicated Pad
    Year of the Trial-Size Dove Bar
    Year of the Perdue Wonderchicken
    Year of the Whisper-Quiet Maytag Dishmaster
    Year of the Yushityu 2007 Mimetic-Resolution-Cartridge-View-Motherboard-Easy-To-Install-Upgrade For Infernatron/InterLace TP Systems For Home, Office Or Mobile (sic)
    Year of Dairy Products from the American Heartland
    Year of the Depend Adult Undergarment
    Year of Glad

  3. These days I run into dates labeled BCE and CE. I believe this means Before Current Era and Current Era, and the timeline is identical to BC and AD. It's not difficult to imagine reasons to be able to use the common Western chronology without explicitly invoking the Christian savior, in Latin.

  4. Hi Bud! Yeah, I oversimplified astronomically when I said people counted years by the Popes. In fact, Dave Cunix would have beat you to the punch to say so, but he's having login troubles.

    It seems to me that before, say, the Industrial Revolution, very few people were educated enough to worry about anything that happened before their parents were born. So it was a moot point.

    Ross, this whole thing came up because recently the BBC decided to switch from BC/AD to BCE/CE. Which is not much of a switch at all, if you think about it. It's not like they went to thirteen four-week months.