After stumbling over putting “2015” on the first dated item I wrote this year, a couple things occurred to me. First, while I usually have unnecessarily fervent views on stylistic choices, I don’t have a strong preference for the American or British convention for dates (month/day/year as opposed to day/month/year). The British way seems more logical (smallest to biggest) while the American way mimics the way most people say dates aloud. Second, I’ve never read a good explanation as to why the different conventions came about. If I were guessing wildly, a path-dependent story related to military convention in one of the world wars would be where I’d start, I think.
For date formats in prose, I think my preferred format for is “5 January 2015,” but I’m not sure I have a good, non-aesthetic reason for it. It sounds overly robotic and bureaucratic if read aloud, but looks nicer on the page and separates numerals, which limits the danger of transposition in typing.