Default language in 7.2

Is there a way to set the standard language for example to Danish?. Has peered into languages.inc.php and changed 'en' to 'dk' even after cookies and cache are removed, remains the site in English

You can do a few things.

1) Go to Settings - Advanced Settings - General

Scroll down to Default Country and change that to your country and Save.

2) You can also go to Settings - Language Settings and import your language and set it up that way. 

You cannot just go into a file and change en to dk. It won't work that way.

Also, if you are using Danish interface language without any additional languages, copying Danish translation to default English would make a trick.