changed default finish_date in Order to shippingdate if available

Layout/default/Emailtemplates/order/int_billing_info.php

@@ -2,7 +2,12 @@
   $term_id = $order->terminations[0]->id;
   $op = OrderProductModel::getFirst(['order_id' => $order->id, 'termination_id' => $term_id]);
   
-  $billing_start = date('U');
+  if($order->finish_date) {
+    $billing_start = $order->finish_date;
+  } else {
+    $billing_start = date('U');
+  }
+  
   if($op->billing_delay) {
     $billing_start = strtotime("+".$op->billing_delay." months");
   }