diff --git a/Models/EditorDoc.php b/Models/EditorDoc.php
index 7d90364..e1aff0b 100755
--- a/Models/EditorDoc.php
+++ b/Models/EditorDoc.php
@@ -75,7 +75,7 @@ class EditorDoc implements \JsonSerializable, ArrayableInterface
      * @var \DateTime
      * @since 1.0.0
      */
-    private \DateTime $createdAt;
+    private \DateTimeImmutable $createdAt;
 
     /**
      * Creator.
@@ -101,7 +101,7 @@ class EditorDoc implements \JsonSerializable, ArrayableInterface
     public function __construct()
     {
         $this->createdBy = new NullAccount();
-        $this->createdAt = new \DateTime('now');
+        $this->createdAt = new \DateTimeImmutable('now');
     }
 
     /**
@@ -163,7 +163,7 @@ class EditorDoc implements \JsonSerializable, ArrayableInterface
      *
      * @since 1.0.0
      */
-    public function getCreatedAt() : \DateTime
+    public function getCreatedAt() : \DateTimeInterface
     {
         return $this->createdAt;
     }
diff --git a/Models/EditorDocMapper.php b/Models/EditorDocMapper.php
index ecbe5a2..bb2e188 100755
--- a/Models/EditorDocMapper.php
+++ b/Models/EditorDocMapper.php
@@ -41,7 +41,7 @@ final class EditorDocMapper extends DataMapperAbstract
         'editor_doc_plain'      => ['name' => 'editor_doc_plain',      'type' => 'string',   'internal' => 'plain'],
         'editor_doc_content'    => ['name' => 'editor_doc_content',    'type' => 'string',   'internal' => 'content'],
         'editor_doc_path'       => ['name' => 'editor_doc_path',       'type' => 'string',   'internal' => 'path'],
-        'editor_doc_created_at' => ['name' => 'editor_doc_created_at', 'type' => 'DateTime', 'internal' => 'createdAt', 'readonly' => true],
+        'editor_doc_created_at' => ['name' => 'editor_doc_created_at', 'type' => 'DateTimeImmutable', 'internal' => 'createdAt', 'readonly' => true],
     ];
 
     /**