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Except BC/AD -> BCE/CE is a label change, not a numbering change, and it's arguably for largely P.C. reasons; conforming to P.C. is the "in" thing. We in America have also changed from Indians to Native Americans to American Indians to Indigenous Peoples to whatever, and N* to Black to Colored to African American to something supposedly unoffensive while still defining the same group.

http://en.wikipedia.org/wiki/Common_Era

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edit in response to edits: I too agree with preferring BC/AD, they're the same size and look more different. BCE/CE both end in "CE", and the similarities between "B" and "E" don't help :\ And I see BCE more-ish in recent history books, but not much outside there (though there aren't qualifiers for most things I read, it's all too recent).

I'm voting for positive values == CE and negative values == BCE. They're already numbered that way, just adopt the frickin' sign instead of the suffix! Nearly everything becomes easier, left-to-right hints at relative age prior to even seeing the number, and parsing from a computer standpoint is as easy as to_i().

> I'm voting for positive values == CE and negative values == BCE. They're already numbered that way, just adopt the frickin' sign instead of the suffix!

Nope, not really. There's no year 0. Neither A.D. nor B.C.--that's because zero wasn't known to the guys who invented this numbering system, and also because those guys counted years with ordinal numbers (first year, second year, etc) and not with cardinal numbers since Christ.

You see the same confusion over death (Friday) and resurrection (Sunday): Jesus rose on the third day, not after three days. (Since the weekdays are not given in the bible directly, you can also find alternative suggestions for the weekdays.)

Disclaimer: Words like Jesus, Christ, death and resurrection are used purely as labels to describe stuff some people believe in. No judgement implied.

I think it's ridiculous to rename dates just to remove their religious connotations, especially when the reference point is still the (slightly inaccurate) birth of Christ. If someone wanted to start with a new system, where year 0 is the Big Bang, that would be reasonable - it would put all dates on the same time scale instead of having to convert between BC and AD. But if you're going to keep the religious reference point, why pretend it's something else? Prejudice is the only reason that I can see.

Of course, when we revise our estimates of when that happened, it would screw everything up again...

I have no problem with people trying to do this in principle. I really don't care enough, but other people can.

The symbol "tau", however, is an especially poor choice for a trigonometric symbol, because it's also used for torque. You won't get many physics teachers to change over if every time you try to calculate a torque from a force and radius, you run into a symbol conflict.

How many symbols aren't in use, though? If you've got a notably better one, the "manifesto" may consider changing, but they seem (to me) to have pretty good reasons for choosing tau.

I'd ideally prefer to pick one that isn't used in angular things. Because non-English, non-Greek glyphs are somewhat underused for this sort of thing, and because of visual similarity to pi, I'd suggest the hebrew Het or Russian л. However, I really have no problem with continuing to use the multi-glyph symbol 2pi.

Too much visual similarity to pi is a recipe for many factor-of-two errors.

Why a multi-glyph symbol 2π when a single-glyph symbol 2π would be better. By creating a new symbol by joining the bottom-right of the 2 to the topleft of the π, we can make a new one-glyph symbol, perhaps put it next to € in Unicode.

And instead of saying two words "Two Pi", we could say it as one word "Twopi", with stress on the first syllable, much like the word "teenager" used to be spoken and written as two words a century ago.

I like the idea of "Twopi". Looks like it could be pronounced like "Toupee". (yes, it'd be a mispronunciation, but people do that)

Do you also favor the almighty interrobang‽

We pronounce the constant as pee in German anyway. (No confusion with bodily fluids there.)

Or we might as well go with dvapee (Russian), or tsveypee (German (zweipi, written so that you can pronounce it the English way and it'll come out ok)).

We can go for pronouncing the thingy pipi. (Though would lead to confusion with bodily fluids in German.)

You know, I really don't care that much about the 2pi thing, but this is just cool enough that I might be able to get behind it.

My first thought exactly. Mechanical engineers and physicists appreciate where Tau is at the moment. But as someone notes, there is always symbol conflicts.

"at the moment"

very funny ;)

I mention torque in the manifesto, but I wasn't specific enough in this case, and I've added an example addressing this issue at http://tauday.com/#sec:four_arguments. The short version is that when necessary you can easily add a subscript to avoid ambiguity, such as tau_R for rotational torque. (Superscripts work, too. Particle physicists deal with pions, which are represented by the letter pi, but all the symbols have superscripts indicating their electric charge. As a result, no one ever confuses them with the number.)

The thing is, torque is a particularly bad thing to conflict with. While you're not using torque every time you work with pi, you usually end up using pi every time you work with torque.

edit: It's much like using i for both sqrt(-1) and for current. Electrical engineers need to use both of these all the time, so they often use j for sqrt(-1) instead.

Or you could use M for moment and stop using tau for torque. Most mechanical engineers talk about moments with M instead of tau.

The electrical engineering thing demonstrates that you're unlikely to get a particular discipline to change its own notation. It would have made much more sense in retrospect to change current to something other than i, but that's not what happened.

As an electrical engineer (by way of physics and math), I'll use any other damn letter that makes sense for current that you want, and try to sway my fellows too. I just haven't seen a good option yet. What have you got?

"c"... no good, speed of light for one; and also current needs good a good alteration for DC vs AC, "c" and "C" look too similar when written by someone else's hand (and "C" is crap in equations anyway since it can look too much like a "("). Current is a flow, but "f" is well used. Any good suggestions?

Agreed. He mentions overloading the pi symbol for the prime counting function but the difference is that you very rarely encounter pi in the prime counting function.

The parent comment is now obsolete; I came up with something even better: http://news.ycombinator.com/item?id=1470379

I would argue though that the torque example is a particularly problematic symbol conflict as any equations involving torque are by definition going to include many, many references to the circle constant. Yes there are other symbol conflicts in math, but usually they are separated by logical fields (you generally are not doing using e when dealing with the charge of an electron constant (except in the case that you are dealing with magnitude of the electric field as a function of distance) and even when you are, it is hardly a problem because you never use the natural logarithmic constant except as a power function).

I think the appropriate change here though would be to change the symbol for torque to say, 'q' or something. Probably not going to happen, but wouldn't be as much of an issue.

I would suggest a change to uppercase Gamma, which looks like a T, kinda. Also, it has always struck me as a looking kind of like a moment arm.

Something like this is bound to happen if mathematics pedagogy moves to tau as the circle constant, which it should. The math department has no motivation to respect physics convention, and the physics department will just have to get in line, eventually.

Or physicists/engineers will do their own thing, as seen by using j = sqrt(-1).

Also, uppercase gamma is already used, too. http://en.wikipedia.org/wiki/Gamma_function

Granted, but interference with mechanical torque is unlikely.

Greek letters are pretty polysemantic in the context of maths and physics.

These arguments are assuming that tau would be a total replacement for pi in all situations. Why not just keep using pi in situations where you are doing calculations with torque?

The point of tau (or pi) is to do calculations with angles. One of the main uses of angles in physics is calculations having to do with torque. Basically, using pi for calculations that might involve torque is giving away one of the situations where tau would be most useful.

This torque issue was really bothering me, and I finally realized why: I was pretty sure I'd already seen torque represented by a letter other than tau. Sure enough, I checked my copy of Introduction to Electrodynamics by David Griffiths, which is a popular (and truly great) intermediate E&M text, and there it was on p. 162: torque written as N = r X F. The same usage appears in several other places in that book, and Introduction to Electrodynamics is a standard text, so I'm confident that other sources use it as well. So we see that the idea of using a letter other than tau for torque is not some theoretical possibility—it has already happened, and in a standard textbook to boot. I've updated the manifesto with a note to this effect at http://tauday.com/#sec:four_arguments.

I realize that this may not convince you, but I urge you to reserve the right to change your mind about tau. After all, I changed my mind about pi. ;-)

And there are only so many letters in the alphabet(s). Although I have to admit common usage hasn't really exhausted the hebrew alphabet, yet.

And when the Chinese finally take over, we will have enough short symbols to last us for millenia.

I remember vaguely from my time using Griffiths' book that he uses a lot of non-standard (or at least not the same as other, more introductory textbooks) notation. He pretty freely reassigns the symbols used by things that you're supposed to understand, in order to free them up for other purposes.

Or at least that's my vague recollection. It's been a few years now since I've cracked open his Electrodynamics. It was a pretty decent book though, better than a lot of textbooks (I kept it and still have my edition around somewhere, something that I didn't do if I thought a textbook was crummy).

Interesting. N may not be such a great symbol to use for torque, because the equation relating it to force and radius is a cross-product. In that context, N often refers to a "normal" vector. Still, it's apparently in use somewhere, which is interesting.

Ugh, I know this is slightly offtopic, but there's nothing more I dislike than B.C.E and C.E. I can understand not trying to promote a Christian-centric worldview, but by only changing the labels, they accomplish nothing. Now, the birth of Christ sets a 'common era,' which arguable makes it _more_ 'offensive' than just acknowledging what happened on that particular day.

The switch to B.C.E. and C.E. is also because the year of Jesus' birth is debated. Some believe he was born in 4 C.E. At least that's what I recall from school many many years ago. Personally, I prefer "B.C." and "A.D." because those two are more different from each other (edit distance of two) than "B.C.E." and "C.E." (edit distance of one, unless you count periods).

Edit: Wikipedia says Jesus was born in 5 B.C. (http://en.wikipedia.org/wiki/Jesus)

While you are correct that most scholars don't believe that Jesus was born in 1 AD, the reason the change was made was to distance scholarship from Christianity.

There is another dating system which aims to get around this, by actually changing the numbers, which is called Before Present (BP). It sets 0 to be January 1, 1950, as an arbitrary date of the present. So, 1500 BP is 450 AD. I see it used most often it dealing with archaeology.

Are you sure that April 20, 2010 isn't 0 BP? :)

Unix epoch had it right. Let's just all count seconds before/after 1 Jan 1970.

A slight complication to this solution is that the length of a year is not exactly divisible to seconds, or even of constant length. So counting seconds is fundamentally different from, though pretty close to, counting years.

Don't forget, though, AD stands for Anno Domini, which means "in the year of our Lord." Which is a little more than just acknowledgement.

The "our" translation is just convention, not actually there in the latin.

Actually, AD is the shortened form for "the year of our Lord". The "Year of our Lord" came first, before the initials.

Why can't we dispense with the annotation completely? BC/BCE counts backwards, so let's just say 1970 or -1970.

edit: posted this before I saw Groxx's reply below

I don't know what you folks are on about. My ddate clearly tells me

<pre>Today is Prickle-Prickle, the 33rd day of Confusion in the YOLD 3176</pre>

Only there is no year zero, by (that) definition. http://en.wikipedia.org/wiki/0_(year)

Nor are BCE and CE all that commonly used.

AD vs. BC: I prefer using CE with negative numbers, as suggested by ISO 8601. E.g., year -30 CE is year 31 BC.

Too many people would get confused, forgetting to substract 1 from the BC-tagged number, or unsure whether to add or substract 1, or wondering if the other person remembered to subtract 1.

I suggest adding 7000 to all dates, as well as using negatives. So...

2010AD -> 9010

1AD -> 7001

1BC -> 7000

31BC -> 6970

5000BC -> 2001 (except people talk about year ranges, not years, when refering to events that far back, so there'd be no confusion with our current AD references)

Or we can just adopt the Discordian Calendar and, by increasing confusion, reduce disharmony.

http://en.wikipedia.org/wiki/Discordian_calendar

Hail Eris!

speaking for US-ians: would the Texas State School Board actually allow the rest of us to switch from BC/AD to BCE/CE? :)

There is no need in "#.".

> It seems like over the past few years we've definitively decided on B.C.E. and C.E. instead.

I don't think that is the case. Amongst recently published works of history that I have read (1st ed. books), from some very reputable publishers (Cambridge, Oxford, UC, etc), I have only seen BC/AD in use.