title: DateTime::format in German (day of the week)
body: <p>I'd like to have a German output from <code>DateTime::format('D, d.m.Y H:i')</code> meaning that instead of 'Sun, ...' I want to get 'So, ...'. I set <code>setlocale(LC_ALL,'de_DE');</code> but this didn't solve the problem.</p>