title: How to edit the ctime of Django?
body: <p>In my Order model:</p>
  
  <pre><code>class Order(models.Model):
      order_num = models.CharField(max_length=128, unique=True)
      ctime = models.DateTimeField(auto_now_add=True)   
      uptime = models.DateTimeField(auto_now=True) 
  </code></pre>
  
  <p>I have <code>ctime</code> you see. </p>
  
  <p>But in my <code>Order</code>'s update APIView:</p>
  
  <pre><code>class OrderUpdateAPIView(UpdateAPIView):
      serializer_class = OrderSerializer
      permission_classes = [IsSuperAdminOrFinanceAdmin]
      queryset = Order.objects.all()
      lookup_field = "order_num" 
  </code></pre>
  
  <p>I can not edit the Order's <code>ctime</code> although the API return success.  </p>