With this in mind, I was a bit taken aback by this sequence of searches:
I couldn't resist. I grabbed the low-hanging fruit offered by Wikipedia:
But I am a suspicious fellow... and almost paranoid of Wikipedia. No matter what Scot McKnight says (see #15), I just don't trust us internet geeks to organically self-correct with enough speed and accuracy to make this whole piecemeal education thing work. So I tried newadvent.org:
That, my good people, is a 25-year discrepancy (I did the math in my head... all the while being distracted by the tabloid accusations of his sordid fall from ascetic ideals; happens to the best of us, I guess). My first thought here was that I had the wrong Marcion. Perhaps there was another guy by this name who attempted to dejudiaze Christianity, reshape the canon, slander the God of the Hebrew Bible, etc. But no, it just seems that there is quite a difference of opinion regarding the date of his birth.
So then, I thought: what I need is a fancy, expensive WUNT monograph that has been vetted by unforgiving experts who revel in the thought of taking a junior colleague down a notch. So I turned to Sebastian Moll's recent monograph: The Arch-Heretic Marcion (2010). Edinburgh graduates can be insufferable miscreants, but they tend to be pretty good scholars, I've found.
Here is what Dr. Moll writes on p. 26:
One of the great things about writing for a blog is that at least one of my readers will be able to enlighten me. Why did Harnack suggest the date of 85 CE? Why was he wrong (if he was)? And why hasn't Scot McKnight or one of you Wikipedia believers self-corrected yet?