diff --git a/src/Core/OAuth/OAuth2/OAuth2AccessToken.php b/src/Core/OAuth/OAuth2/OAuth2AccessToken.php
index 255b6ad9..a0d8fb02 100644
--- a/src/Core/OAuth/OAuth2/OAuth2AccessToken.php
+++ b/src/Core/OAuth/OAuth2/OAuth2AccessToken.php
@@ -359,6 +359,6 @@ public function updateAccessToken($tokenExpiresTime, $refreshToken, $refreshToke
      * @return string
      */
     private function getDateFromSeconds($seconds){
-      return date('Y/m/d H:i:s', $seconds);
+      return date('Y-m-d\TH:i:s.Z\Z', $seconds);
     }
 }