Form element title is not displaying translation
I think you need  add t() in #markup and translate the string 'Estimated time:'

$form['informacie_o_incidente']['field_incident_doba'] = array(
  '#title' =&gt; t('Estimated time'),
  '#markup' =&gt; '&lt;div class="control-group form-item"&gt;&lt;label class="control-label"&gt;'.t('Estimated time:').'&lt;/label&gt;&lt;div id="field_incident_doba_wrapper" class="controls"&gt;'.$doba.'&lt;/div&gt;&lt;/div&gt;',
);