diff --git a/src/Bundle/ChillCalendarBundle/Entity/RemoteCalendarTrait.php b/src/Bundle/ChillCalendarBundle/Entity/RemoteCalendarTrait.php
index 4196de35a..9e162541d 100644
--- a/src/Bundle/ChillCalendarBundle/Entity/RemoteCalendarTrait.php
+++ b/src/Bundle/ChillCalendarBundle/Entity/RemoteCalendarTrait.php
@@ -15,6 +15,14 @@ use Doctrine\ORM\Mapping as ORM;
 
 trait RemoteCalendarTrait
 {
+    /**
+     * If true, the changes won't be enqueued to remote.
+     *
+     * This is required to prevent update loop: a persist trigger an event creation on remote,
+     * which in turn change remoteId and, in turn, trigger an update change, ...
+     */
+    public bool $preventEnqueueChanges = false;
+
     /**
      * @ORM\Column(type="json", options={"default": "[]"}, nullable=false)
      */
@@ -25,14 +33,6 @@ trait RemoteCalendarTrait
      */
     private string $remoteId = '';
 
-    /**
-     * If true, the changes won't be enqueued to remote
-     *
-     * This is required to prevent update loop: a persist trigger an event creation on remote,
-     * which in turn change remoteId and, in turn, trigger an update change, ...
-     */
-    public bool $preventEnqueueChanges = false;
-
     public function addRemoteAttributes(array $remoteAttributes): self
     {
         $this->remoteAttributes = array_merge($this->remoteAttributes, $remoteAttributes);
diff --git a/src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraph/RemoteEventConverter.php b/src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraph/RemoteEventConverter.php
index 409a30240..569ec2f56 100644
--- a/src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraph/RemoteEventConverter.php
+++ b/src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraph/RemoteEventConverter.php
@@ -107,6 +107,11 @@ class RemoteEventConverter
         );
     }
 
+    public function getLastModifiedDate(array $event): DateTimeImmutable
+    {
+        return DateTimeImmutable::createFromFormat(self::REMOTE_DATETIMEZONE_FORMAT, $event['lastModifiedDateTime']);
+    }
+
     /**
      * Return a string which format a DateTime to string. To be used in POST requests,.
      */
diff --git a/src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraphRemoteCalendarConnector.php b/src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraphRemoteCalendarConnector.php
index ade4baa28..db02b4903 100644
--- a/src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraphRemoteCalendarConnector.php
+++ b/src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraphRemoteCalendarConnector.php
@@ -19,7 +19,6 @@ use Chill\CalendarBundle\RemoteCalendar\Connector\MSGraph\OnBehalfOfUserTokenSto
 use Chill\CalendarBundle\RemoteCalendar\Connector\MSGraph\RemoteEventConverter;
 use Chill\MainBundle\Entity\User;
 use DateTimeImmutable;
-use Exception;
 use Psr\Log\LoggerInterface;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Response;
@@ -110,9 +109,10 @@ class MSGraphRemoteCalendarConnector implements RemoteCalendarConnectorInterface
     public function syncCalendarRange(CalendarRange $calendarRange): void
     {
         if ($calendarRange->hasRemoteId()) {
-            throw new Exception('update existing not implemented');
+            $this->updateRemoteCalendarRange($calendarRange);
+        } else {
+            $this->createRemoteCalendarRange($calendarRange);
         }
-        $this->createRemoteCalendarRange($calendarRange);
     }
 
     private function createRemoteCalendarRange(CalendarRange $calendarRange): void
@@ -148,11 +148,9 @@ class MSGraphRemoteCalendarConnector implements RemoteCalendarConnectorInterface
             throw $e;
         }
 
-        dump($event);
-
         $calendarRange->setRemoteId($event['id'])
             ->addRemoteAttributes([
-                'lastModifiedDateTime' => (DateTimeImmutable::createFromFormat(RemoteEventConverter::REMOTE_DATETIMEZONE_FORMAT, $event['lastModifiedDateTime']))->getTimestamp(),
+                'lastModifiedDateTime' => $this->remoteEventConverter->getLastModifiedDate($event)->getTimestamp(),
                 'changeKey' => $event['changeKey'],
             ]);
     }
@@ -201,4 +199,69 @@ class MSGraphRemoteCalendarConnector implements RemoteCalendarConnectorInterface
             $response['value'][0]['scheduleItems']
         );
     }
+
+    private function updateRemoteCalendarRange(CalendarRange $calendarRange): void
+    {
+        $userId = $this->mapCalendarToUser->getUserId($calendarRange->getUser());
+        $calendarId = $this->mapCalendarToUser->getCalendarId($calendarRange->getUser());
+
+        if (null === $userId || null === $calendarId) {
+            $this->logger->warning('user does not have userId nor calendarId', [
+                'user_id' => $calendarRange->getUser()->getId(),
+                'calendar_range_id' => $calendarRange->getId(),
+            ]);
+
+            return;
+        }
+
+        try {
+            $event = $this->machineHttpClient->request(
+                'GET',
+                'users/' . $userId . '/calendar/events/' . $calendarRange->getRemoteId()
+            )->toArray();
+        } catch (ClientExceptionInterface $e) {
+            $this->logger->warning('Could not get event from calendar', [
+                'calendar_range_id' => $calendarRange->getId(),
+                'calendar_range_remote_id' => $calendarRange->getRemoteId(),
+            ]);
+
+            throw $e;
+        }
+
+        if ($this->remoteEventConverter->getLastModifiedDate($event)->getTimestamp() > $calendarRange->getUpdatedAt()->getTimestamp()) {
+            $this->logger->info('Skip updating as the lastModified date seems more fresh than the database one', [
+                'calendar_range_id' => $calendarRange->getId(),
+                'calendar_range_remote_id' => $calendarRange->getRemoteId(),
+                'db_last_updated' => $calendarRange->getUpdatedAt()->getTimestamp(),
+                'remote_last_updated' => $this->remoteEventConverter->getLastModifiedDate($event)->getTimestamp(),
+            ]);
+
+            return;
+        }
+
+        $eventData = $this->remoteEventConverter->calendarRangeToEvent($calendarRange);
+
+        try {
+            $event = $this->machineHttpClient->request(
+                'PATCH',
+                'users/' . $userId . '/calendar/events/' . $calendarRange->getRemoteId(),
+                [
+                    'json' => $eventData,
+                ]
+            )->toArray();
+        } catch (ClientExceptionInterface $e) {
+            $this->logger->warning('could not update calendar range to remote', [
+                'exception' => $e->getTraceAsString(),
+                'calendarRangeId' => $calendarRange->getId(),
+            ]);
+
+            throw $e;
+        }
+
+        $calendarRange
+            ->addRemoteAttributes([
+                'lastModifiedDateTime' => $this->remoteEventConverter->getLastModifiedDate($event)->getTimestamp(),
+                'changeKey' => $event['changeKey'],
+            ]);
+    }
 }