diff --git a/lib/Providers/Personal/CollectionResource.php b/lib/Providers/Personal/CollectionResource.php
index c0f1b33..ab1ab11 100644
--- a/lib/Providers/Personal/CollectionResource.php
+++ b/lib/Providers/Personal/CollectionResource.php
@@ -11,6 +11,7 @@ namespace KTXM\ProviderLocalChrono\Providers\Personal;
 
 use KTXF\Chrono\Collection\CollectionMutableAbstract;
 use KTXF\Resource\Identifier\CollectionIdentifier;
+use KTXF\Utile\Timestamp;
 
 class CollectionResource extends CollectionMutableAbstract {
 
@@ -73,8 +74,8 @@ class CollectionResource extends CollectionMutableAbstract {
 			'rank' => $properties->getRank(),
 			'visibility' => $properties->getVisibility(),
 			'color' => $properties->getColor(),
-			'createdOn' => $this->data[self::PROPERTY_CREATED] ?? null,
-			'modifiedOn' => $this->data[self::PROPERTY_MODIFIED] ?? null,
+			'createdOn' => Timestamp::normalize($this->data[self::PROPERTY_CREATED] ?? null),
+			'modifiedOn' => Timestamp::normalize($this->data[self::PROPERTY_MODIFIED] ?? null),
 			'signature' => $this->data[self::PROPERTY_SIGNATURE] ?? null,
 			'enabled' => $this->collectionEnabled,
 		], static fn($value) => $value !== null);
diff --git a/lib/Providers/Personal/EntityResource.php b/lib/Providers/Personal/EntityResource.php
index 10d46da..1ad984f 100644
--- a/lib/Providers/Personal/EntityResource.php
+++ b/lib/Providers/Personal/EntityResource.php
@@ -11,6 +11,7 @@ namespace KTXM\ProviderLocalChrono\Providers\Personal;
 
 use KTXF\Chrono\Entity\EntityMutableAbstract;
 use KTXF\Chrono\Event\EventObject;
+use KTXF\Utile\Timestamp;
 
 class EntityResource extends EntityMutableAbstract {
 
@@ -49,8 +50,8 @@ class EntityResource extends EntityMutableAbstract {
 			'uid' => $this->userId,
 			'cid' => $this->collection(),
 			'eid' => $this->identifier(),
-			'createdOn' => $this->data[self::PROPERTY_CREATED] ?? date('c'),
-			'modifiedOn' => date('c'),
+			'createdOn' => Timestamp::normalize($this->data[self::PROPERTY_CREATED] ?? null),
+			'modifiedOn' => Timestamp::normalize($this->data[self::PROPERTY_MODIFIED] ?? null),
 		], static fn($value) => $value !== null);
 
 		$document = array_merge($document, $this->getProperties()->toStore());