diff --git a/lib/Alchemy/Phrasea/Controller/Api/V1Controller.php b/lib/Alchemy/Phrasea/Controller/Api/V1Controller.php
index 540c6104b0..126611ef2b 100644
--- a/lib/Alchemy/Phrasea/Controller/Api/V1Controller.php
+++ b/lib/Alchemy/Phrasea/Controller/Api/V1Controller.php
@@ -61,6 +61,7 @@ use Alchemy\Phrasea\SearchEngine\SearchEngineResult;
 use Alchemy\Phrasea\SearchEngine\SearchEngineSuggestion;
 use Alchemy\Phrasea\Status\StatusStructure;
 use Alchemy\Phrasea\TaskManager\LiveInformation;
+use Alchemy\Phrasea\Utilities\NullableDateTime;
 use Doctrine\ORM\EntityManager;
 use Symfony\Component\Form\Form;
 use Symfony\Component\HttpFoundation\File\UploadedFile;
@@ -138,10 +139,10 @@ class V1Controller extends Controller
             'pid'            => $data['process-id'],
             'jobId'          => $task->getJobId(),
             'period'         => $task->getPeriod(),
-            'last_exec_time' => $task->getLastExecution() ? $task->getLastExecution()->format(DATE_ATOM) : null,
-            'last_execution' => $task->getLastExecution() ? $task->getLastExecution()->format(DATE_ATOM) : null,
-            'updated'        => $task->getUpdated() ? $task->getUpdated()->format(DATE_ATOM) : null,
-            'created'        => $task->getCreated() ? $task->getCreated()->format(DATE_ATOM) : null,
+            'last_exec_time' => NullableDateTime::format($task->getLastExecution()),
+            'last_execution' => NullableDateTime::format($task->getLastExecution()),
+            'updated'        => NullableDateTime::format($task->getUpdated()),
+            'created'        => NullableDateTime::format($task->getCreated()),
             'auto_start'     => $task->getStatus() === Task::STATUS_STARTED,
             'crashed'        => $task->getCrashed(),
         ];
@@ -709,9 +710,9 @@ class V1Controller extends Controller
             'position'        => $user->getActivity() ?: null,
             'company'         => $user->getCompany() ?: null,
             'geoname_id'      => $user->getGeonameId() ?: null,
-            'last_connection' => $user->getLastConnection() ? $user->getLastConnection()->format(DATE_ATOM) : null,
-            'created_on'      => $user->getCreated() ? $user->getCreated()->format(DATE_ATOM) : null,
-            'updated_on'      => $user->getUpdated() ? $user->getUpdated()->format(DATE_ATOM) : null,
+            'last_connection' => NullableDateTime::format($user->getLastConnection()),
+            'created_on'      => NullableDateTime::format($user->getCreated()),
+            'updated_on'      => NullableDateTime::format($user->getUpdated()),
             'locale'          => $user->getLocale() ?: null,
         ];
     }
@@ -1466,11 +1467,7 @@ class V1Controller extends Controller
                 ];
             }, iterator_to_array($basket->getValidation()->getParticipants()));
 
-            $expires_on_atom = $basket->getValidation()->getExpires();
-
-            if ($expires_on_atom instanceof \DateTime) {
-                $expires_on_atom = $expires_on_atom->format(DATE_ATOM);
-            }
+            $expires_on_atom = NullableDateTime::format($basket->getValidation()->getExpires());
 
             $ret = array_merge([
                 'validation_users'          => $users,
diff --git a/lib/Alchemy/Phrasea/Feed/Formatter/AtomFormatter.php b/lib/Alchemy/Phrasea/Feed/Formatter/AtomFormatter.php
index be7533249d..5371f97a41 100644
--- a/lib/Alchemy/Phrasea/Feed/Formatter/AtomFormatter.php
+++ b/lib/Alchemy/Phrasea/Feed/Formatter/AtomFormatter.php
@@ -17,6 +17,7 @@ use Alchemy\Phrasea\Feed\FeedInterface;
 use Alchemy\Phrasea\Feed\Link\FeedLink;
 use Alchemy\Phrasea\Feed\Link\LinkGeneratorCollection;
 use Alchemy\Phrasea\Model\Entities\User;
+use Alchemy\Phrasea\Utilities\NullableDateTime;
 use Symfony\Component\HttpFoundation\Response;
 
 class AtomFormatter extends FeedFormatterAbstract implements FeedFormatterInterface
@@ -48,8 +49,6 @@ class AtomFormatter extends FeedFormatterAbstract implements FeedFormatterInterf
      */
     public function format(FeedInterface $feed, $page, User $user = null, $generator = 'Phraseanet', Application $app = null)
     {
-        $updated_on = $feed->getUpdatedOn();
-
         $document = new \DOMDocument('1.0', 'UTF-8');
         $document->formatOutput = true;
         $document->standalone = true;
@@ -59,8 +58,7 @@ class AtomFormatter extends FeedFormatterAbstract implements FeedFormatterInterf
         $root->setAttribute('xmlns:media', 'http://search.yahoo.com/mrss/');
 
         $this->addTag($document, $root, 'title', $feed->getTitle());
-        if ($updated_on instanceof \DateTime) {
-            $updated_on = $updated_on->format(DATE_ATOM);
+        if (null !== $updated_on = NullableDateTime::format($feed->getUpdatedOn())) {
             $this->addTag($document, $root, 'updated', $updated_on);
         }
 
diff --git a/lib/Alchemy/Phrasea/Feed/Formatter/CoolirisFormatter.php b/lib/Alchemy/Phrasea/Feed/Formatter/CoolirisFormatter.php
index 936a5aba87..a7f81addf9 100644
--- a/lib/Alchemy/Phrasea/Feed/Formatter/CoolirisFormatter.php
+++ b/lib/Alchemy/Phrasea/Feed/Formatter/CoolirisFormatter.php
@@ -19,6 +19,7 @@ use Alchemy\Phrasea\Model\Entities\FeedEntry;
 use Alchemy\Phrasea\Model\Entities\FeedItem;
 use Alchemy\Phrasea\Feed\Link\LinkGeneratorCollection;
 use Alchemy\Phrasea\Model\Entities\User;
+use Alchemy\Phrasea\Utilities\NullableDateTime;
 use DateTime;
 use Symfony\Component\HttpFoundation\Response;
 
@@ -52,8 +53,6 @@ class CoolirisFormatter extends FeedFormatterAbstract implements FeedFormatterIn
      */
     public function format(FeedInterface $feed, $page, User $user = null, $generator = 'Phraseanet', Application $app = null)
     {
-        $updated_on = $feed->getUpdatedOn();
-
         $doc = new \DOMDocument('1.0', 'UTF-8');
         $doc->formatOutput = true;
         $doc->standalone = true;
@@ -89,8 +88,7 @@ class CoolirisFormatter extends FeedFormatterAbstract implements FeedFormatterIn
             $this->addTag($doc, $channel, 'managingEditor', $this->managingEditor);
         if (isset($this->webMaster))
             $this->addTag($doc, $channel, 'webMaster', $this->webMaster);
-        if ($updated_on instanceof DateTime) {
-            $updated_on = $updated_on->format(DATE_RFC2822);
+        if (null !== $updated_on = NullableDateTime::format($feed->getUpdatedOn(), DATE_RFC2822)) {
             $this->addTag($doc, $channel, 'pubDate', $updated_on);
         }
         if (isset($this->lastBuildDate) && $this->lastBuildDate instanceof DateTime) {
diff --git a/lib/Alchemy/Phrasea/Feed/Formatter/RssFormatter.php b/lib/Alchemy/Phrasea/Feed/Formatter/RssFormatter.php
index ec892d2fc3..9e5a923470 100644
--- a/lib/Alchemy/Phrasea/Feed/Formatter/RssFormatter.php
+++ b/lib/Alchemy/Phrasea/Feed/Formatter/RssFormatter.php
@@ -17,6 +17,7 @@ use Alchemy\Phrasea\Feed\Link\FeedLink;
 use Alchemy\Phrasea\Feed\Link\LinkGeneratorCollection;
 use Alchemy\Phrasea\Feed\RSS\FeedRSSImage;
 use Alchemy\Phrasea\Model\Entities\User;
+use Alchemy\Phrasea\Utilities\NullableDateTime;
 use Symfony\Component\HttpFoundation\Response;
 use Alchemy\Phrasea\Model\Entities\FeedEntry;
 use Alchemy\Phrasea\Feed\Link\FeedLinkGenerator;
@@ -51,8 +52,6 @@ class RssFormatter extends FeedFormatterAbstract implements FeedFormatterInterfa
      */
     public function format(FeedInterface $feed, $page, User $user = null, $generator = 'Phraseanet', Application $app = null)
     {
-        $updated_on = $feed->getUpdatedOn();
-
         $next = $prev = null;
 
         if ($feed->hasPage($page + 1, self::PAGE_SIZE)) {
@@ -104,11 +103,10 @@ class RssFormatter extends FeedFormatterAbstract implements FeedFormatterInterfa
             $this->addTag($doc, $channel, 'managingEditor', $this->managingEditor);
         if (isset($this->webMaster))
             $this->addTag($doc, $channel, 'webMaster', $this->webMaster);
-        if ($updated_on instanceof \DateTime) {
-            $updated_on = $updated_on->format(DATE_RFC2822);
+        if (null !== $updated_on = NullableDateTime::format($feed->getUpdatedOn(), DATE_RFC2822)) {
             $this->addTag($doc, $channel, 'pubDate', $updated_on);
         }
-        if (isset($this->lastBuildDate) && $this->lastBuildDate instanceof DateTime) {
+        if (isset($this->lastBuildDate) && $this->lastBuildDate instanceof \DateTime) {
             $last_build = $this->lastBuildDate->format(DATE_RFC2822);
             $this->addTag($doc, $channel, 'lastBuildDate', $last_build);
         }
diff --git a/lib/Alchemy/Phrasea/Order/Controller/ApiOrderController.php b/lib/Alchemy/Phrasea/Order/Controller/ApiOrderController.php
index 06f2ca60a1..f11b3f2202 100644
--- a/lib/Alchemy/Phrasea/Order/Controller/ApiOrderController.php
+++ b/lib/Alchemy/Phrasea/Order/Controller/ApiOrderController.php
@@ -94,8 +94,8 @@ class ApiOrderController extends BaseOrderController
         $pager = new Pagerfanta(new DoctrineORMAdapter($builder, false));
         $pager->setCurrentPage($page);
         $pager->setMaxPerPage($perPage);
-        $paginator = new PagerfantaPaginatorAdapter($pager, $routeGenerator);
-        $resource->setPaginator($paginator);
+
+        $resource->setPaginator(new PagerfantaPaginatorAdapter($pager, $routeGenerator));
 
         return $this->returnResourceResponse($request, $fractal, $resource);
     }
diff --git a/lib/Alchemy/Phrasea/Utilities/NullableDateTime.php b/lib/Alchemy/Phrasea/Utilities/NullableDateTime.php
new file mode 100644
index 0000000000..6f47da81c7
--- /dev/null
+++ b/lib/Alchemy/Phrasea/Utilities/NullableDateTime.php
@@ -0,0 +1,19 @@
+<?php
+/*
+ * This file is part of Phraseanet
+ *
+ * (c) 2005-2016 Alchemy
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Alchemy\Phrasea\Utilities;
+
+final class NullableDateTime
+{
+    public static function format(\DateTime $dateTime = null, $format = DATE_ATOM, $default = null)
+    {
+        return $dateTime ? $dateTime->format($format) : $default;
+    }
+}
diff --git a/lib/classes/ACL.php b/lib/classes/ACL.php
index 649a781528..f5f62f4cb5 100644
--- a/lib/classes/ACL.php
+++ b/lib/classes/ACL.php
@@ -26,6 +26,7 @@ use Alchemy\Phrasea\Core\Event\Acl\SysadminChangedEvent;
 use Alchemy\Phrasea\Model\Entities\User;
 use Alchemy\Phrasea\Model\RecordInterface;
 use Alchemy\Phrasea\Model\RecordReferenceInterface;
+use Alchemy\Phrasea\Utilities\NullableDateTime;
 use Doctrine\DBAL\DBALException;
 
 
@@ -1706,10 +1707,10 @@ class ACL implements cache_cacheableInterface
         }
 
         $params = [
-            ':usr_id'      => $this->user->getId()
-            , ':base_id'     => $base_id
-            , 'limited_from' => ($limit_from ? $limit_from->format(DATE_ISO8601) : null)
-            , 'limited_to'   => ($limit_to ? $limit_to->format(DATE_ISO8601) : null)
+            ':usr_id' => $this->user->getId(),
+            ':base_id' => $base_id,
+            'limited_from' => NullableDateTime::format($limit_from, DATE_ISO8601),
+            'limited_to' => NullableDateTime::format($limit_to, DATE_ISO8601),
         ];
 
         $stmt = $this->app->getApplicationBox()->get_connection()->prepare($sql);
diff --git a/lib/classes/Bridge/Element.php b/lib/classes/Bridge/Element.php
index 4283e7f9eb..5a81808e55 100644
--- a/lib/classes/Bridge/Element.php
+++ b/lib/classes/Bridge/Element.php
@@ -10,6 +10,7 @@
  */
 
 use Alchemy\Phrasea\Application;
+use Alchemy\Phrasea\Utilities\NullableDateTime;
 
 class Bridge_Element
 {
@@ -383,9 +384,9 @@ class Bridge_Element
             SET uploaded_on = :uploaded_on, updated_on = :update WHERE id = :id';
 
         $params = [
-            ':uploaded_on' => $this->uploaded_on ? $this->uploaded_on->format(DATE_ISO8601) : null
-            , ':id'          => $this->id
-            , ':update'      => $this->updated_on->format(DATE_ISO8601)
+            ':uploaded_on' => NullableDateTime::format($this->uploaded_on, DATE_ISO8601),
+            ':id' => $this->id,
+            ':update' => $this->updated_on->format(DATE_ISO8601),
         ];
 
         $stmt = $this->app->getApplicationBox()->get_connection()->prepare($sql);
diff --git a/lib/classes/media/subdef.php b/lib/classes/media/subdef.php
index 0f167e426e..f37a154df0 100644
--- a/lib/classes/media/subdef.php
+++ b/lib/classes/media/subdef.php
@@ -11,6 +11,7 @@
 
 use Alchemy\Phrasea\Application;
 use Alchemy\Phrasea\Http\StaticFile\Symlink\SymLinker;
+use Alchemy\Phrasea\Utilities\NullableDateTime;
 use Guzzle\Http\Url;
 use MediaAlchemyst\Alchemyst;
 use MediaVorus\Media\MediaInterface;
@@ -206,8 +207,8 @@ SQL;
             'physically_present' => $this->is_physically_present,
             'is_substituted' => $this->is_substituted,
             'subdef_id' => $this->subdef_id,
-            'updated_on' => $this->modification_date ? $this->modification_date->format(DATE_ATOM) : '',
-            'created_on' => $this->creation_date ? $this->creation_date->format(DATE_ATOM) : '',
+            'updated_on' => NullableDateTime::format($this->modification_date),
+            'created_on' => NullableDateTime::format($this->creation_date),
             'etag' => $this->etag,
             'url' => (string)$this->url,
         ];