OK, seems that Mendix team has intended something else with change method. At least for me it remains unknown due to very poor documentation ![sad sad](https://forum.mendix.com/widgets/CKEditorForMendix/widget/lib/plugins/smiley/images/sad_smile.png)
In this case a I have replaced change with setValue method and it does its job.
obj.setValue(getContext(), "createdDate", new Date());