title: How to create a timestamp on submit in Django class based views for Update?
body: <p>I'm new to class based views in Django and was using a simple UpdateView CBV. The view has many fields that is being displayed on a template, except one; the <code>Date field</code>. How do I add a timestamp to this field? The timestamp should be added only the first time the object is created. From the next time onwards, it should only show the timestamp that was added the first time. This is my code:</p>
  
  <pre><code>class ReviewsEdit(UpdateView):
      model = ProductReview
      fields = ['title', 'body', 'score', 'responder_name', 'response']     
      template_name = 'review_system/review_edit.html'
      context_object_name = 'review'
  </code></pre>
  
  <p>The <code>ProductReview</code> model has all the above fields with another Date field, I'd like to save it with timestamp data when the submit button was clicked - only if it is blank when submitting. Is this possible with CBV?</p>