(EC) There is no 'officially sanctioned one', whatever you mean by that. See Wikipedia:Manual of Style/Dates and numbers. Both styles are acceptable, the only thing that is required is consistency within an article and don't change style without a good reason. In terms of preference, we do the same as we do with varieties of English. In cases where the subject is clearly tied to one country, as is the case here (to the US), we follow the style that is most common there which is month day, year.