"Is ISO 8601 really beyond comprehension for most of the population?"
Absolutely! I have had to program date-related code, and I am familiar with the differences between US and European date formats, and I have never heard of ISO 8601 before today.
The average person from the US will assume that 2015-04-03 is March 4th, 2015, while a typical person from Europe will assume it's April 3rd, 2015. You're still thinking in the context of a computer programmer, not the context of a user.
I'm a bit surprised that you "have had to program date-related code" and "have never heard of ISO 8601", because it is practically the standard for date formatting. I know non-programmers from different countries including US/UK/EU, and although they probably haven't heard of ISO 8601 either, they have absolutely no trouble understanding YYYY-MM-DD HH:MM:SS. This is a very small sample size and probably not representative, but I doubt many people would attempt to parse it as YYYY-DD-MM.
I'm in the US and I've never heard of 2015-04-03 being interpreted as March 4. I just see the standard interpretation as logical, since it's coarse (year) to fine (day).
Well, on the other hand, 'customary' US order is MM-DD-YYYY based on how we normally (verbally) say dates.
Honestly, its perfectly ok for an application to use whatever standard date format - as long as its clear and consistent within the application - at least in the context of North America, where everything is a mishmash of whatever standards you can imagine.
Hell, .Net datetimes specifically allow you to output in whatever format the current OS default is set to (or you can choose your own).
No, like July 4th. Or July 5th. Or October 31st. The 4th of July is a notable exception, and the GP's point of how we "normally (verbally) say dates" stands.
I'm not sure I can really speak to how the "average person from the US" would deal with 2015-04-03, but two data points:
1. Everyone I personally know would know that that meant 4/3.
2. 4/3 in US usage is April 3rd. As I understand it, it's March 4th in European usage, but you say they have no problem with YYYY-MM-DD. I tend to suspect that you sort of half-learned that "US dates are backwards from European dates" and then misapplied that lesson here.
> As I understand it, it's March 4th in European usage
British usage. For Germans, 4/3 means 1.33333. April 3rd is 3.4. here. If you do i18n, do NOT assume there is one consistent European convention. Either use ISO 8601 or a library that understands country conventions.
Absolutely! I have had to program date-related code, and I am familiar with the differences between US and European date formats, and I have never heard of ISO 8601 before today.
The average person from the US will assume that 2015-04-03 is March 4th, 2015, while a typical person from Europe will assume it's April 3rd, 2015. You're still thinking in the context of a computer programmer, not the context of a user.