diff --git a/clock.module b/clock.module
index ecbb519..500d669 100755
--- a/clock.module
+++ b/clock.module
@@ -108,10 +108,8 @@ function clock_block_configure($delta = '') {
     // the formatted time is displayed in the wrong, old time zone.
     $date_types = array();
     foreach (system_get_date_types() as $date_type => $info) {
-      // Each date format type has a corresponding variable. If it is not set,
-      // get the list of date formats for that type and use the first one.
-        $date_format = variable_get('date_format_' . $date_type, key(system_get_date_formats($date_type)));
-        $date_types[$date_type] = $info['title'] . ' (' . date_format_date(date_now(_clock_get_timezone(TRUE)), 'custom', $date_format) . ')';
+      $date_format = _clock_get_date_format($date_type);
+      $date_types[$date_type] = $info['title'] . ' (' . date_format_date(date_now(_clock_get_timezone(TRUE)), 'custom', $date_format) . ')';
     }
     $form['date_type'] = array(
       '#type' => 'radios',
@@ -203,14 +201,26 @@ function _clock_get_timezone($date_format_date = FALSE) {
 /**
  * Gets the correct date format.
  *
+ * @param $date_type
+ *   (optional) The date type to return the date format for. If omitted, uses
+ *   the date type which is set for the clock.
+ *
  * @return
  *   The date format of the date type used for the clock.
  */
-function _clock_get_date_format() {
-  $date_type = variable_get('clock_date_type', 'long');
-  // Each date format type has a corresponding variable. If it is not set, get
-  // the list of date formats for that type and use the first one.
-  $date_format = variable_get('date_format_' . $date_type, key(system_get_date_formats($date_type)));
+function _clock_get_date_format($date_type = NULL) {
+  if (!isset($date_type)) {
+    $date_type = variable_get('clock_date_type', 'long');
+  }
+  // Each date format type has a corresponding variable. If it is not set,
+  // get the list of date formats for that type and use the first one. We
+  // cannot use the fallback directly in variable_get(), because
+  // system_get_date_formats() can return FALSE for custom date types. In
+  // that case, the variable is always set, though.
+  $date_format = variable_get('date_format_' . $date_type, NULL);
+  if (!isset($date_format)) {
+    $date_format = key(system_get_date_formats($date_type));
+  }
   return $date_format;
 }