Change the default language of a node
Of course.

I would do it this way:

1) Install of module devel. 
Drupal7

2) go to drupal/devel/php
Of course.

Drupal8


in the textarea add:



  //please, change the nid of your node


use Drupal\node\Entity\Node;    

$nid = 1;
$node = Node::load($nid);
$node-&gt;get('langcode')-&gt;value = 'da';
$node-&gt;save();


In Drupal7

$nid=1;
$node=node_load($nid);
$node-&gt;language='da';
node_save($node);