diff --git a/api/runtime.php b/api/runtime.php
index 6feeb6c..8efe3c7 100644
--- a/api/runtime.php
+++ b/api/runtime.php
@@ -829,13 +829,13 @@ class runtime extends cora\api {
    *
    * @return string The UTC datetime string.
    */
-  private function get_utc_datetime($local_datetime, $local_time_zone) {
+  private function get_utc_datetime($local_datetime, $local_time_zone, $format = 'Y-m-d H:i:s') {
     $local_time_zone = new DateTimeZone($local_time_zone);
     $utc_time_zone = new DateTimeZone('UTC');
     $date_time = new DateTime($local_datetime, $local_time_zone);
     $date_time->setTimezone($utc_time_zone);
 
-    return $date_time->format('Y-m-d H:i:s');
+    return $date_time->format($format);
   }
 
   /**
@@ -846,13 +846,13 @@ class runtime extends cora\api {
    *
    * @return string The UTC datetime string.
    */
-  private function get_local_datetime($utc_datetime, $local_time_zone) {
+  private function get_local_datetime($utc_datetime, $local_time_zone, $format = 'Y-m-d H:i:s') {
     $local_time_zone = new DateTimeZone($local_time_zone);
     $utc_time_zone = new DateTimeZone('UTC');
     $date_time = new DateTime($utc_datetime, $utc_time_zone);
     $date_time->setTimezone($local_time_zone);
 
-    return $date_time->format('Y-m-d H:i:s');
+    return $date_time->format($format);
   }
 
   /**