After my recent Utopian calendar post, let's follow-up with something more practical. What date does 10/11/12 denote? 10. Nov. 2012? Or 11. Oct. 2012? Or maybe even 2010-Nov-12 or even more surprising 2010-Dec-11?
In the USA, the second guess is probably most plausible. In Germany, France, and countries nearby, on the other hand, such a question would be quite unlikely to arise, because the slash (/) is not usually used to delimit dates. This is a very good thing, because if someone writes a day in their country's most common format, this allows us to also guess the intended order of numbers and thus the meaning. If I see 05.04.80 I assume German syntax and semantics and read it as a day in April.
Given this convenient feature of syntax, I find it very disturbing that some programs offer to format dates using American slashes for separation but a non-American Day/Month ordering. It seems like they tried to adapt to a different cultures, but did it so half-baken that they only made things worse.
To make things simple again, I am using a few very easy rules to make all my dates unambiguous, no matter in which country I happen to stay, who is addressed by my writings, and which format I am following (my own or the recipient's, if they are different).
Rule One: Always use different syntax for different ordering.
Rule One Prime: Avoid / since it has been abused to much. Better use . when starting with the day or use - when writing in ISO-format.
This first rule already removes most of ambiguity, but it doesn't it always make very intuitive to read dates. For example, it's easy for me to process "1. March" and just as easy to read "March 1st" or "Mar-01", but there seems to be something wrong about March 1st 2013.
Therefore Rule Two: always write a date with increasing order of "day. month. year" or completely decreasing order "year-month-day". So I can choose to write 1. March 2013 or 2013-Mar-01, but not any other order.
Note that this scales well for incomplete dates such as "March 2013" (or "2013-Mar") as well as date-time combinations such as 13:45 on 13.Mar.2013 or 2013-03-13T13:45.
Finally Rule Three: although the above is quite unambiguous already, whenever I am in an ambiguous context such as a country with a different convention from mine, I also prefer to spell out years with all four digits and spell out months with at least three letters. The latter might seem a little antique or overly literary for a person who likes numbers a lot. But I think that words just are more helpful here.
And after all, every month is special for the number of days it has, so we can't meaningfully talk about dates anyway, unless we know all the months. If I ask you, for example, to hang out on 28.08. or a week later, you need to decode 08. to August in order to calculate, that a week later is 04.09. (This becomes even funner if I propose 28.08. or the Sunday after that, because you need to know which year I am talking of. But, you know, in The World Calendar, 28. Aug is always a Tuesday and the next Sunday is always 02.Sept. ;-))