There is an Auto language detection at forums.gentoo.org. When forums interface is not English and no user is currently logged in, the date format template is incorrectly taken from somewhere but current lang_main.php file. The DOW and month language is still correct, though. The correct date format is stored at localized lang_main.php $lang['DATE_FORMAT']
Maybe that's wrong date format to take - it's without time of day in all the language files... then the correct one is to be added ;)
Where does the incorrect date format show up? Most dates are shown with the time included, even when not logged in. Or this this just a matter of the default date format not being correct for certain languages?, e.g. Russian. If so could you provide us with the correct date format?
I did "curl -H 'Accept-Language: de' -L forums.gentoo.org" and all dates appeared to be in German language.