If the question is one of reckoning years, I don’t see how the “duration of a year” can be ignored. That’s what a year is.
Exactly. You are attempting to make your argument regarding the number line by appealing to a semantic convention of the language and ignoring the reality that the first year is zero. When filling out medical forms for kids’ vaccinations, the age is always indicated by spaces for Years____ and Months___. Before the first birthday, I always write Years_0_ and Months_6_. I never wrote Years_FIRST YEAR_.
What? My argument about the number line, with respect to calendar years, has nothing at all to do with the conventions of language. Certainly not the age convention which as I noted is not universal anyway.
If we look at your kid’s age on the number line, six months is in the span between the 0 point (birth) and the +1 point (“first birthday,” or first anniversary of birth). That the kid’s age is 0y./6m., or 0.5 years, with a numeral 0 at the front, does not mean that the whole year is a “Year Zero.” You, I, everybody calls that the “first year,” because it is, in fact, the first year. Zero is a point. None of the kid’s first year occupies that point.
The point you were trying to defend was
If you mean that something done by most Americans isn’t “common”, then I guess we just have different definitions of that term. Then again, you capitalized it, so perhaps you were talking about some specific standard named “Common” but you didn’t cite it, so I assume that was a typo.
If that’s the case, they’re counting from a different zero, which nullifies the point.
The point of having a year zero is to be able to find the interval between two years (or between two times, expressed as real numbers) by subtracting them, without regard to whether they span the starting point. With BC/AD and BCE/CE, you can’t do this. That’s all.
I believe that’s not standardized by C, but rather, defined by the floating point hardware on your machine (which most likely conforms to IEEE floating point standards). So, blame IEEE, not C.
The same zero, in different directions.
That’s an awfully small computational convenience for which to embark upon a terminological revision to billions of documents. Never minding the aesthetic/conceptual absurdity which I seem unable to explain to a couple people.
I tend to agree with this in the overall. I suspect that revising the calendar at a time when the entire world of business, (with millions of ledgers and schedules and the programs to support them), had already adopted a consistent calendar (unlike previous centuries where business was localized and the calendars were inconsistent as one moved across national or regional boundaries), would be an unnecessary waste.
Well, it would have been easier to explain if you had been right, of course. 
I don’t want to Nitpick OR to hijack the thread, but am happy to do BOTH! 
… Your belief is incorrect.
You are making no sense. I’m certainly not going to withdraw a suggestion that makes perfect and complete sense. Let me try explaining it this way:
The year 2013 is not a discrete point. Midnight on December 31 of 2013 is a discrete point. Let’s call it “last moment 2013.”
To find the elapsed time between two dates on the AD/CE calendar, you merely subtract one from the other. Last moment 2013 is two years after last moment 2011, because 2013-2011=2. The exact same thing works with the BC/BCE calendar.
You can’t, however, apply this between an AD/CE date and a BC/BCE date. Last moment 2 AD/CE is three years after last moment 2 BC/BCE, which makes no sense.
Creating a proper timeline makes that problem go away. Last moment 2 would be four years after last moment -2 because 2 minus (-2) is 4. Those four years would be -1, 0, 1, and 2.
The concept of a continuous timeline is used in darned near everything. 2 degrees Celsius is four degrees warmer than -2 degrees Celsius. 2 miles north of here is 4 miles away from 2 miles south of here. My proposal fixes the calendar to work like the rest of the world, and uses sensible mathematics with a single scale instead of two.
Speaking as a Catholic…
I’ve known some Jews who use “BCE” and “ACE,” but I don’t see any indication that this practice is becoming more common. Rather, the great majority of non-Christians are just going on using “BC” and “AD” without giving any real thought to what those abbreviations mean. And even if they do know what the abbreviations mean, it doesn’t seem to bother them.
And really, why should it? We Christians have used the names “Tuesday,” Wednesday," “Thursday” and “Friday” for centuries without worrying a bit that those days were named for the ancient Norse deities Tyr, Odin, Thor and Freya (or that Saturday was named in honor of the Roman god Saturn). We’ve accepted that some of our months were named after Roman deities like Janus and Juno, and never demanded that those names be changed.
Whether you believe in Jesus or not, most of the world has long been using a calendar that treats his birth as a starting point. Why change now?
It’s pretty easy to use terms while forgetting or ignoring their religious origins. Relax!
Germanic. Norse are germanic, slightly different names for the Gods, but still. Tuesday comes from Tiu and Wednesday from Wodan.
We ought to pick a new starting point so as not to privilege Christianity, which is not even a majority of the world’s people, is it? In a lot of early American documents, you see dates written like “In the year of our lord 1823, and of the United States the 47th.” Starting from American independence, this is year 237 AI. Washington was born in 44 BI. Which I personally think would be a cool system to use, except that again it privileges only a part of the world’s population. We would need to pick a starting date with a universal meaning. Something scientific. The birth of Isaac Newton in 1642, which would make this the year 371 AN. Or the date we first split the atom, 1942, which would make this the year 71 AA. It’s easy to think of events that are of worldwide significance, like the invention of agriculture—but there’s no precise date for that. The suggestion to date the birth of agriculture from 8000 BCE is again based on the Christian reckoning. While plenty of significant specific dates are available, how many of them have worldwide significance? Anyway, it should be based on science, something relating to planet Earth, and not somebody’s religion.
Again, is calling the 5th day of the week “Thursday” (meaning “Thor’s Day”) giving any kind of “privilege” to pagans?
Is calling the 6th month “June,” in honor of the goddess Juno, giving any kind of privilege to pagans?
Of COURSE NOT! So relax.
As a practical matter, almost everyone in the world, from Richard Dawkins to Benjamin Netanyahu to the Dalai Lama to Nidal Hasan accepts that it’s the year 2013, and almost nobody really cares what the starting point is.