diff --git a/Models/Report.php b/Models/Report.php
index d1dcafb..492e4f0 100755
--- a/Models/Report.php
+++ b/Models/Report.php
@@ -76,7 +76,7 @@ class Report implements \JsonSerializable
      * @var \DateTime
      * @since 1.0.0
      */
-    protected \DateTime $createdAt;
+    protected \DateTimeImmutable $createdAt;
 
     /**
      * Report created by.
@@ -110,7 +110,7 @@ class Report implements \JsonSerializable
     public function __construct()
     {
         $this->createdBy = new NullAccount();
-        $this->createdAt = new \DateTime('now');
+        $this->createdAt = new \DateTimeImmutable('now');
         $this->template  = new NullTemplate();
         $this->source    = new NullCollection();
     }
@@ -238,7 +238,7 @@ class Report implements \JsonSerializable
      *
      * @since 1.0.0
      */
-    public function getCreatedAt() : \DateTime
+    public function getCreatedAt() : \DateTimeInterface
     {
         return $this->createdAt;
     }
diff --git a/Models/ReportMapper.php b/Models/ReportMapper.php
index 6b1360b..988f336 100755
--- a/Models/ReportMapper.php
+++ b/Models/ReportMapper.php
@@ -42,7 +42,7 @@ final class ReportMapper extends DataMapperAbstract
         'helper_report_media'    => ['name' => 'helper_report_media',    'type' => 'int',      'internal' => 'source'],
         'helper_report_template' => ['name' => 'helper_report_template', 'type' => 'int',      'internal' => 'template'],
         'helper_report_creator'  => ['name' => 'helper_report_creator',  'type' => 'int',      'internal' => 'createdBy', 'readonly' => true],
-        'helper_report_created'  => ['name' => 'helper_report_created',  'type' => 'DateTime', 'internal' => 'createdAt', 'readonly' => true],
+        'helper_report_created'  => ['name' => 'helper_report_created',  'type' => 'DateTimeImmutable', 'internal' => 'createdAt', 'readonly' => true],
     ];
 
     /**
diff --git a/Models/Template.php b/Models/Template.php
index b334941..4aaad51 100755
--- a/Models/Template.php
+++ b/Models/Template.php
@@ -102,7 +102,7 @@ class Template implements \JsonSerializable
      * @var \DateTime
      * @since 1.0.0
      */
-    protected \DateTime $createdAt;
+    protected \DateTimeImmutable $createdAt;
 
     /**
      * Template created by.
@@ -151,7 +151,7 @@ class Template implements \JsonSerializable
      */
     public function __construct()
     {
-        $this->createdAt = new \DateTime('now');
+        $this->createdAt = new \DateTimeImmutable('now');
         $this->unit      = new NullUnit();
         $this->source    = new NullCollection();
         $this->createdBy = new NullAccount();
@@ -350,7 +350,7 @@ class Template implements \JsonSerializable
      *
      * @since 1.0.0
      */
-    public function getCreatedAt() : \DateTime
+    public function getCreatedAt() : \DateTimeInterface
     {
         return $this->createdAt;
     }
diff --git a/Models/TemplateMapper.php b/Models/TemplateMapper.php
index 80ae184..17da882 100755
--- a/Models/TemplateMapper.php
+++ b/Models/TemplateMapper.php
@@ -48,7 +48,7 @@ final class TemplateMapper extends DataMapperAbstract
         'helper_template_media'      => ['name' => 'helper_template_media',       'type' => 'int',      'internal' => 'source'],
         'helper_template_creator'    => ['name' => 'helper_template_creator',     'type' => 'int',      'internal' => 'createdBy'],
         'helper_template_unit'       => ['name' => 'helper_template_unit',        'type' => 'int',      'internal' => 'unit'],
-        'helper_template_created'    => ['name' => 'helper_template_created',     'type' => 'DateTime', 'internal' => 'createdAt'],
+        'helper_template_created'    => ['name' => 'helper_template_created',     'type' => 'DateTimeImmutable', 'internal' => 'createdAt'],
     ];
 
     /**