diff --git a/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php b/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php
index ed8a9b7ba8a1..04862e5d80f7 100644
--- a/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php
+++ b/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php
@@ -396,7 +396,7 @@ protected function addTimestampsToAttachment(array $record, $exists = false)
         if ($this->using) {
             $pivotModel = new $this->using;
 
-            $fresh = $fresh->format($pivotModel->getDateFormat());
+            $fresh = $pivotModel->fromDateTime($fresh);
         }
 
         if (! $exists && $this->hasPivotColumn($this->createdAt())) {