diff --git a/Models/Report.php b/Models/Report.php
index 492e4f0..b2d7c71 100755
--- a/Models/Report.php
+++ b/Models/Report.php
@@ -234,11 +234,11 @@ class Report implements \JsonSerializable
     /**
      * Get created datetime
      *
-     * @return \DateTime
+     * @return \DateTimeImmutable
      *
      * @since 1.0.0
      */
-    public function getCreatedAt() : \DateTimeInterface
+    public function getCreatedAt() : \DateTimeImmutable
     {
         return $this->createdAt;
     }
diff --git a/Models/Template.php b/Models/Template.php
index 4aaad51..72ff47d 100755
--- a/Models/Template.php
+++ b/Models/Template.php
@@ -346,11 +346,11 @@ class Template implements \JsonSerializable
     /**
      * Get created date
      *
-     * @return \DateTime
+     * @return \DateTimeImmutable
      *
      * @since 1.0.0
      */
-    public function getCreatedAt() : \DateTimeInterface
+    public function getCreatedAt() : \DateTimeImmutable
     {
         return $this->createdAt;
     }