diff --git a/src/Entity/Attachments/Attachment.php b/src/Entity/Attachments/Attachment.php
index 78789001..61f370e4 100644
--- a/src/Entity/Attachments/Attachment.php
+++ b/src/Entity/Attachments/Attachment.php
@@ -156,6 +156,12 @@ abstract class Attachment extends AbstractNamedDBElement
     #[Groups(['attachment:read', 'attachment_write'])]
     protected ?AttachmentType $attachment_type = null;
 
+    #[Groups(['attachment:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['attachment:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     public function __construct()
     {
         //parent::__construct();
diff --git a/src/Entity/Attachments/AttachmentType.php b/src/Entity/Attachments/AttachmentType.php
index 3afe0192..d4cc7b25 100644
--- a/src/Entity/Attachments/AttachmentType.php
+++ b/src/Entity/Attachments/AttachmentType.php
@@ -76,7 +76,7 @@ use Symfony\Component\Validator\Constraints as Assert;
     uriVariables: [
         'id' => new Link(fromProperty: 'children', fromClass: AttachmentType::class)
     ],
-    normalizationContext: ['groups' => ['footprint:read', 'api:basic:read'], 'openapi_definition_name' => 'Read']
+    normalizationContext: ['groups' => ['attachment_type:read', 'api:basic:read'], 'openapi_definition_name' => 'Read']
 )]
 #[ApiFilter(PropertyFilter::class)]
 #[ApiFilter(LikeFilter::class, properties: ["name", "comment"])]
@@ -96,7 +96,7 @@ class AttachmentType extends AbstractStructuralDBElement
 
     /**
      * @var string A comma separated list of file types, which are allowed for attachment files.
-     * Must be in the format of <input type=file> accept attribute
+     * Must be in the format of <pre><input type=file></pre> accept attribute
      * (See https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/file#Unique_file_type_specifiers).
      */
     #[ORM\Column(type: Types::TEXT)]
@@ -132,6 +132,12 @@ class AttachmentType extends AbstractStructuralDBElement
     #[ORM\OneToMany(targetEntity: Attachment::class, mappedBy: 'attachment_type')]
     protected Collection $attachments_with_type;
 
+    #[Groups(['attachment_type:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['attachment_type:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     public function __construct()
     {
         $this->children = new ArrayCollection();
diff --git a/src/Entity/Parts/Category.php b/src/Entity/Parts/Category.php
index 3c15b86c..b1dc8c97 100644
--- a/src/Entity/Parts/Category.php
+++ b/src/Entity/Parts/Category.php
@@ -177,6 +177,12 @@ class Category extends AbstractPartsContainingDBElement
     #[ORM\OrderBy(['group' => 'ASC', 'name' => 'ASC'])]
     protected Collection $parameters;
 
+    #[Groups(['category:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['category:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     public function getPartnameHint(): string
     {
         return $this->partname_hint;
diff --git a/src/Entity/Parts/Footprint.php b/src/Entity/Parts/Footprint.php
index f65f5031..2cdf9fba 100644
--- a/src/Entity/Parts/Footprint.php
+++ b/src/Entity/Parts/Footprint.php
@@ -129,6 +129,12 @@ class Footprint extends AbstractPartsContainingDBElement
     #[Groups(['footprint:read', 'footprint:write'])]
     protected Collection $parameters;
 
+    #[Groups(['footprint:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['footprint:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     /****************************************
      * Getters
      ****************************************/
diff --git a/src/Entity/Parts/MeasurementUnit.php b/src/Entity/Parts/MeasurementUnit.php
index 4ee4176b..f9f45ca5 100644
--- a/src/Entity/Parts/MeasurementUnit.php
+++ b/src/Entity/Parts/MeasurementUnit.php
@@ -150,6 +150,12 @@ class MeasurementUnit extends AbstractPartsContainingDBElement
     #[Groups(['measurement_unit:read', 'measurement_unit:write'])]
     protected Collection $parameters;
 
+    #[Groups(['measurement_unit:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['measurement_unit:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     /**
      * @return string
      */
diff --git a/src/Entity/Parts/Part.php b/src/Entity/Parts/Part.php
index d53ac8f6..fa01d212 100644
--- a/src/Entity/Parts/Part.php
+++ b/src/Entity/Parts/Part.php
@@ -150,6 +150,12 @@ class Part extends AttachmentContainingDBElement
     #[Groups(['part:read', 'part:write'])]
     protected ?Attachment $master_picture_attachment = null;
 
+    #[Groups(['part:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['part:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     public function __construct()
     {
         $this->attachments = new ArrayCollection();
diff --git a/src/Entity/Parts/StorageLocation.php b/src/Entity/Parts/StorageLocation.php
index 338e77d9..3a7847d9 100644
--- a/src/Entity/Parts/StorageLocation.php
+++ b/src/Entity/Parts/StorageLocation.php
@@ -164,6 +164,12 @@ class StorageLocation extends AbstractPartsContainingDBElement
     #[Groups(['location:read', 'location:write'])]
     protected ?Attachment $master_picture_attachment = null;
 
+    #[Groups(['location:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['location:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     /********************************************************************************
      *
      *   Getters
diff --git a/src/Entity/PriceInformations/Currency.php b/src/Entity/PriceInformations/Currency.php
index 0713c8d7..a108feeb 100644
--- a/src/Entity/PriceInformations/Currency.php
+++ b/src/Entity/PriceInformations/Currency.php
@@ -36,8 +36,6 @@ use ApiPlatform\Metadata\Post;
 use ApiPlatform\Serializer\Filter\PropertyFilter;
 use App\ApiPlatform\Filter\LikeFilter;
 use App\Entity\Attachments\Attachment;
-use App\Entity\Attachments\AttachmentTypeAttachment;
-use App\Entity\Parts\Footprint;
 use App\Repository\CurrencyRepository;
 use Doctrine\DBAL\Types\Types;
 use App\Entity\Attachments\CurrencyAttachment;
@@ -152,6 +150,12 @@ class Currency extends AbstractStructuralDBElement
     #[ORM\OneToMany(targetEntity: Pricedetail::class, mappedBy: 'currency')]
     protected Collection $pricedetails;
 
+    #[Groups(['currency:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['currency:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     public function __construct()
     {
         $this->children = new ArrayCollection();
diff --git a/src/Entity/ProjectSystem/Project.php b/src/Entity/ProjectSystem/Project.php
index 68cbc0b9..81b1fc09 100644
--- a/src/Entity/ProjectSystem/Project.php
+++ b/src/Entity/ProjectSystem/Project.php
@@ -153,6 +153,12 @@ class Project extends AbstractStructuralDBElement
     #[Groups(['project:read', 'project:write'])]
     protected Collection $parameters;
 
+    #[Groups(['project:read'])]
+    protected ?\DateTimeInterface $addedDate = null;
+    #[Groups(['project:read'])]
+    protected ?\DateTimeInterface $lastModified = null;
+
+
     /********************************************************************************
      *
      *   Getters