I've added a site-wide configuration option for whether an English-language wiki should display dates in American (Mar 3, 2003) or International format (3 Mar 2003).
Set "$wgAmericanDates = true;" in LocalSettings to use the American format. English Wikipedia has been set to use American dates for now to maintain the status quo, as I have no interest in arguments about the desirability of one or other other style. However the new option may be of interest for third-party sites.
The date & time code needs some general overhauling... timezone data can be gotten from the browser via JavaScript (but it's roundabout, as we can't talk to it directly, and of course not always available), and we need to support half-hour timezones (parts of Australia, India, elsewhere).
Display of dates in YYYY-MM-DD format should also be an available option, and we will certainly want user-selectability on these things, as well as sensible ways of setting defaults and sniffing locale info from browsers where possible and appropriate.
The generation of date/timestamps in ~~~~ sigs is also currently a mess; it uses a locale-based function and doesn't integrate with our language files.
-- brion vibber (brion @ pobox.com)