diff --git a/Models/Promotion.php b/Models/Promotion.php
index f6cf70d..ca0921c 100755
--- a/Models/Promotion.php
+++ b/Models/Promotion.php
@@ -78,7 +78,7 @@ class Promotion
      * @var \DateTime
      * @since 1.0.0
      */
-    private \DateTime $createdAt;
+    private \DateTimeImmutable $createdAt;
 
     /**
      * Created by.
@@ -102,7 +102,7 @@ class Promotion
         $this->start = new \DateTime('now');
         $this->end   = new \DateTime('now');
         $this->end->modify('+1 month');
-        $this->createdAt = new \DateTime('now');
+        $this->createdAt = new \DateTimeImmutable('now');
         $this->createdBy = new NullAccount();
 
         $this->calendar = new Calendar();
@@ -482,7 +482,7 @@ class Promotion
      *
      * @since 1.0.0
      */
-    public function getCreatedAt() : \DateTime
+    public function getCreatedAt() : \DateTimeInterface
     {
         return $this->createdAt;
     }
diff --git a/Models/PromotionMapper.php b/Models/PromotionMapper.php
index c9f1b8c..4107a78 100755
--- a/Models/PromotionMapper.php
+++ b/Models/PromotionMapper.php
@@ -49,7 +49,7 @@ final class PromotionMapper extends DataMapperAbstract
         'marketing_promotion_progress'      => ['name' => 'marketing_promotion_progress',      'type' => 'int',          'internal' => 'progress'],
         'marketing_promotion_progress_type' => ['name' => 'marketing_promotion_progress_type', 'type' => 'int',          'internal' => 'progressType'],
         'marketing_promotion_created_by'    => ['name' => 'marketing_promotion_created_by',    'type' => 'int',          'internal' => 'createdBy', 'readonly' => true],
-        'marketing_promotion_created_at'    => ['name' => 'marketing_promotion_created_at',    'type' => 'DateTime',     'internal' => 'createdAt', 'readonly' => true],
+        'marketing_promotion_created_at'    => ['name' => 'marketing_promotion_created_at',    'type' => 'DateTimeImmutable', 'internal' => 'createdAt', 'readonly' => true],
     ];
 
     /**