diff --git a/src/Handler/Shipment/GetShipmentHandler.php b/src/Handler/Shipment/GetShipmentHandler.php
index 4c2878a..532372b 100644
--- a/src/Handler/Shipment/GetShipmentHandler.php
+++ b/src/Handler/Shipment/GetShipmentHandler.php
@@ -37,6 +37,10 @@ public function __invoke(GetShipment $getShipment): Shipment
         ]);
 
         $response = $response->getBody()->json();
+
+        // Current return includes milliseconds: 2018-12-20T11:34:50.237+01:00
+        // Convert this timestamp into ISO 8601 format.
+        $response['shipmentDate'] = (new \DateTime($response['shipmentDate']))->format(\DateTime::ATOM);
         $response['shipmentItems'] = array_map(static function (array $item) {
             $item['latestDeliveryDate'] = (new \DateTime($item['latestDeliveryDate']))->format('Y-m-d');