diff --git a/Models/Event.php b/Models/Event.php
index 76ae390..81499ad 100755
--- a/Models/Event.php
+++ b/Models/Event.php
@@ -507,11 +507,11 @@ class Event
     /**
      * get created at
      *
-     * @return \DateTime
+     * @return \DateTimeImmutable
      *
      * @since 1.0.0
      */
-    public function getCreatedAt() : \DateTimeInterface
+    public function getCreatedAt() : \DateTimeImmutable
     {
         return $this->createdAt;
     }