How to change rendering of div order in a field? It appears that the module label help is not compatible with Date fields. It allows you to enter text, but it does not display.

I found out that in the div with class description should be above div id edit-field-geboortedatum-und-0-value instead of below

How to achieve this? Should I change a weight key in something?
You can use $form['#after_build'] to modify a form. Put below element at the end of your hook_form function.

$form['#after_build'][] = 'FORM_NAME_after_build'; //Calls function


After build function to change the position of DIV

function FORM_NAME_after_build($form, $form_state) {
  drupal_add_js('jQuery(document).ready(function ($) {
    $("#edit-field-geboortedatum-und-0-value").insertAfter($(".description"));
  });', array('type' =&gt; 'inline', 'scope' =&gt; 'footer', 'weight' =&gt; 5));

  return $form;
}