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My kids pointed out that there was a mistake on the Roman Numeral clock I recently purchased... four I's instead of "IV". I hadn't even noticed.

Actually, using four I's is not a mistake...although the real story is anybody's guess. I believe the general consensus is that it is more aesthetically pleasing and "balancing" by using the four I's. Here's the 'straight dope':

They do it that way because that's the way they've always done it, at least as far back as 1550, and probably earlier. Many clock historians claim that IIII is supposed to provide artistic balance, since you mentally pair it off with VIII on the other side of the dial. (Presumably you see how the otherwise economical IV would have trouble holding its own in this respect.) The only problem with this theory is that the Romans apparently never used IV--it's a relatively modern invention. It's possible, in other words, that old-time clock makers used IIII because it was considered perfectly proper usage for all purposes, horological or otherwise, at the time. My friend David Feldman, in his book "Why Do Clocks Run Clockwise," cites an expert who says medieval clockmakers used IIII so as not to confuse the illiterate. You could count, "One, two, three, four! Hey, it's four o'clock!" Whereas having to subtract I from V to arrive at the same result was beyond your mental capabilities. Well, maybe. But let's think about this. The peasants couldn't handle IV, but somehow the IX for 9 posed no problems? Did only literate people go out after eight o'clock? Actually, as I read Dave more closely, he seems to be saying that at one time clockmakers used VIIII for 9. OK, but why are we using IIII and IX NOW? Tragically, we may never know the truth. History can be like that.

It goes on even more.... found at http://www.straightdope.com/classics/a2_153.html

Actually it's not a mistake the Roman's wrote it IIII because IV was an abbreviation for Jove or Jupiter their supreme god. It was considered sacrilegious to write 4 as IV even though that became the rule later on when Jove had lost his importance.

Thinkin' Gal says: "My kids pointed out that there was a mistake on the Roman Numeral clock I recently purchased... four I's instead of 'IV'."

And ZinGirl adds: "Actually, using four I's is not a mistake...although the real story is anybody's guess."

ZinGirl is correct, but here's the rest of the story.

When Roman Numerals were originally introduced, there was no value or significance to any given digit or symbol's position in a number. That means that IV and VI both had a value of 6. Such a number system is called a "symbol" weighted system. The only thing that adds value is the symbol.

But in a later development, an attempt was made to "modernize" the Roman Numerals system by adding the concept of "position weighting" where now one had to take into account the position of each symbol relative to the others in order to determine the actual value of a number. By the rules then established for position weighting in the Roman Numeral system, the number IV was thus deemed to have a value of 4 and VI was deemed to have a value of 6.

Which Roman Numeral system is the proper one to use today? Well actually neither, but when it is used the general usage is the modern (or position weighted) one, but for some very formal applications (like your clock), you can still find a few people reverting to the original system.

The change to position weighted was done in a belated attempt to keep the Roman Numeral system "competitive" with the more modern and mathematically useful "place" (not position) weighted systems that were then just beginning to gain acceptance in that area of the world. Place weighted number system are what we use in everyday life today. In our system, each symbol (or digit) has a value that must be multiplied by its position (or column) in the number. Thus when we see the number 1,973 we know that the symbol "7" has a value of 70, and the symbol "9" has a value of 900.

Performing higher forms of math using a symbol weighted is nearly impossible. For example, would you care to calculate the natural log of "V" for me? It was only with the introduction of the place weighted system that such calculations became a reasonable task. Without that development, we never would have left the dark ages and seen the Age of Reason and the development of science. Basically, without it, you would not exist today.

As an interesting aside (for a nerd that is) is that the biggest impediment in the development of a place weighted number system was the invention of a type of digit that had never existed before (because it had never been needed before) and that was the digit zero. (Q: Hey Achmed, what's holding up that new number system of yours? A: Oh, nothing!)(Nerd humor)

So now that I've proven beyond doubt that you owe your existence to "nothing", I'll say good night! Regards,

Boot Hill

That's not a mistake.

That is the way they did it in the old days. How old is this clock?

My kids pointed out that there was a mistake on the Roman Numeral clock I recently purchased... four I's instead of "IV". I hadn't even noticed.

IIII has been used for IV in the clockmaking biz for centuries. This is the only place where IIII means IV.