Why did the mm/dd/yy format for writing dates become the standard in the U.S., as compared to the dd/mm/yy format in most of the rest of the world?
month-day-year was an acceptable form in 19th century Britain.
I think both formats suck. To eliminate confusion I always use characters for the month, e.g.
11-Jun-04
Same with me. For numbers, I just use the ISO standard: it’s the only one with the year first. 2004-06-11.
Nahh. Roman numerals for the month. 18.vii.1956
That only eliminates confusion if all the readers speak the same language, since the “characters for the month” are different in various languages.
Sunspace’s example, using the ISO (International) standard works in all countries that use the 0…9 digits for numbers.
(Plus it proceeds in a logical largest-to-smallest manner: Century Year Month Day.)
Yea, but that still sucks. Does that refer to June 11th or November 6th?
This format:
11-Jun-04
Is 100% foolproof.
It’s already been mentioned that language is a problem. And in any case, is your example 2004, or 2011? 
You gotta have some standards.
To reiterate GorillaMan’s point, does 11-Jun-04 refer to June 4, 2011, or to June 11, 2004? There’s always a bigger fool.
We keep up with “which way is best?” and this’ll be sent straight to IMHO. I’d be interested in seeing a good answer to the question in the OP (how did it come to be MM/DD/YY in the U.S.?), as I’ve often wondered this myself. GorillaMan got us started by pointing out that it used to be this way in the U.K. as well. Maybe we can ammend the question to:
When and why did the U.K. change over to DD/MM/YY?
Worldwide, how are the different methods preferred?
P.S. MM/DD/YY is the best 
My point wasn’t that the UK changed over, but that there was no conformity. As standards developed, the USA went one way and the UK the other. I don’t think there’s any ‘explanation’, it just happened that way.
Aww, you’ll never fight ignorance with that attitude, young man. 
Here in God’s country (Oz,) we use DD/MM/CCYY which equates to the following:
To me, it is easier to remember:
The nth day of the nth month of the year in question…
I have worked internationally for nearly 20 years. I always write out the month and usually 4 digits for the year. The US system of month day year just lends itself to confusion, especially to anyone else where the standard is year month day or day month year.
The different formats in the UK ans USA seem related to the spoken date format; most people in the UK will speak most dates in the format “The fifth of December”, whereas it is my impression that on the other side of the pond, it is more common to say “December fifth” (there are exceptions to this, I’m sure).
Is the spoken parallel here:
-Imaginary (on my part)?
-Coincidental?
-The cause?
-The effect?
I use military standards for both date and time, and I invariably catch hell for doing so. You’d think that if I wrote down 12 Jun 04, 1659 it would be easy to figure out. Alas, they can’t, so I have to change everything to suit their lack of math skills.
The OPs question was really a variation on “Why are people dumb?”, to which I can honestly say that I have no idea, although it annoys the hell out of me.
I am wondering if you are a DBA because that point was driven home to me very strongly through Oracle.
We were expanding an Oracle application to other countries, and it started erroring out when we went to a different NLS envronment. It took me about three weeks and 80% of my sanity to finally figure out that it was the month abbreviations crapping out where a case statment had been coded to read a number and throw in the string.
"You’d think that if I wrote down 12 Jun 04, 1659 it would be easy to figure out. "
I can count, but I don’t get it. ‘1659’ = 12/06/04?
Next is an ‘IMHO’ - and so I risk this thread being deported. I think the most likely answer so far is the literarl translation of what people say:
Here in the UK someone will say ‘The thirteenth of June two thousand and four’
Where as across the pond they’d say ‘June thirteenth two thousand and four’
Those are written down differently and so the abbreviation is also different.
The YYYY/MM/DD and optionally HH:MM:SS format where the numbers are ordered from most significant digit to least is useful because it can be stored as an ordinary number and correctly sorted without resorting to special date routines. The last company I worked for used an ERP system that stored dates that way. The crippling drawback to storing dates as plain text was that an invalid date could be stored which really threw a spanner in the works when pulling data to a data warehouse that used true date format fields.
I think he means 1659 = 4:59 PM