Changing date and time, Twentythirteen

Ok, I realize this has probably been asked a lot of times before, but I can’t for the life of me find a straight and clear answer to this question.

Above my WordPress blogposts, it has the date stamp of that post. Currently it says, f.e.:

“March 18, 2014”

I need it to say:

“18 maart 2014”

So far I have been able to translate ‘March’ into ‘maart’ using the locale.php file in the wp-includes folder. But I can’t find whatever file or code it is that controls the order in which the elements are placed. I found a separate section in locale.php that seemed to be about the date, time and date/time order (had the F j, Y thing going on), so I changed that. But that didn’t do the trick.

I also looked in the twentythirteen.pot file, but I couldn’t find anything related to post dates (just archive and so on).

I’ve searched a few resources (Translating WordPress and php date page) but none of them make it very clear what file I need to be editing or what code needs adding/changing.

I’m using a custom childtheme of Twentythirteen. Can anyone help me?