diff --git a/core/lib/Drupal/Core/Datetime/DrupalDateTime.php b/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
index de6c0f8..ffd9b99 100644
--- a/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
+++ b/core/lib/Drupal/Core/Datetime/DrupalDateTime.php
@@ -124,7 +124,7 @@ public function format($format, $settings = array()) {
     $settings['calendar'] = !empty($settings['calendar']) ? $settings['calendar'] : $this->calendar;
     $settings['langcode'] = !empty($settings['langcode']) ? $settings['langcode'] : $this->langcode;
     $settings['country'] = !empty($settings['country']) ? $settings['country'] : $this->country;
-
+    $settings['format_string_type'] = $format_string_type;
     // Format the date and catch errors.
     try {
 
@@ -142,7 +142,7 @@ public function format($format, $settings = array()) {
         // Paired backslashes are isolated to prevent errors in
         // read-ahead evaluation. The read-ahead expression ensures that
         // A matches, but not \A.
-        $format = preg_replace(array('/\\\\\\\\/', '/(?<!\\\\)([AaeDlMTF])/'), array("\xEF\\\\\\\\\xFF", "\xEF\\\\\$1\$1\xFF"), $format);
+        //$format = preg_replace(array('/\\\\\\\\/', '/(?<!\\\\)([AaeDlMTF])/'), array("\xEF\\\\\\\\\xFF", "\xEF\\\\\$1\$1\xFF"), $format);
 
         // Call date_format().
         $format = parent::format($format);
diff --git a/core/modules/datetime/datetime.module b/core/modules/datetime/datetime.module
index 0da06cb..9d1916d 100644
--- a/core/modules/datetime/datetime.module
+++ b/core/modules/datetime/datetime.module
@@ -50,6 +50,7 @@ function datetime_element_info() {
     '#theme' => 'datetime_form',
     '#theme_wrappers' => array('datetime_wrapper'),
     '#date_date_format' => $date_format,
+    '#date_format_string_type' => $format_type,
     '#date_date_element' => 'date',
     '#date_date_callbacks' => array(),
     '#date_time_format' => $time_format,
@@ -383,7 +384,7 @@ function template_preprocess_datetime_wrapper(&$variables) {
  *   The form element whose value has been processed.
  */
 function datetime_datetime_form_process($element, &$form_state) {
-
+  $format_settings = array('format_string_type' => $element['#date_format_string_type']);
   // The value callback has populated the #value array.
   $date = !empty($element['#value']['object']) ? $element['#value']['object'] : NULL;
 
@@ -403,7 +404,7 @@ function datetime_datetime_form_process($element, &$form_state) {
   if ($element['#date_date_element'] != 'none') {
 
     $date_format = $element['#date_date_element'] != 'none' ? datetime_html5_format('date', $element) : '';
-    $date_value = !empty($date) ? $date->format($date_format) : $element['#value']['date'];
+    $date_value = !empty($date) ? $date->format($date_format, $format_settings) : $element['#value']['date'];
 
     // Creating format examples on every individual date item is messy, and
     // placeholders are invalid for HTML5 date and datetime, so an example
@@ -422,8 +423,8 @@ function datetime_datetime_form_process($element, &$form_state) {
       $html5_max->setDate($range[1], 12, 31)->setTime(23, 59, 59);
 
       $extra_attributes += array(
-        'min' => $html5_min->format($date_format),
-        'max' => $html5_max->format($date_format),
+        'min' => $html5_min->format($date_format, $format_settings),
+        'max' => $html5_max->format($date_format, $format_settings),
       );
     }
 
@@ -450,7 +451,7 @@ function datetime_datetime_form_process($element, &$form_state) {
   if ($element['#date_time_element'] != 'none') {
 
     $time_format = $element['#date_time_element'] != 'none' ? datetime_html5_format('time', $element) : '';
-    $time_value = !empty($date) ? $date->format($time_format) : $element['#value']['time'];
+    $time_value = !empty($date) ? $date->format($time_format, $format_settings) : $element['#value']['time'];
 
     // Adds the HTML5 attributes.
     $extra_attributes = array(
@@ -523,8 +524,8 @@ function form_type_datetime_value($element, $input = FALSE) {
     $date = $element['#default_value'];
     if ($date instanceOf DrupalDateTime && !$date->hasErrors()) {
       $input = array(
-        'date'   => $date->format($element['#date_date_format']),
-        'time'   => $date->format($element['#date_time_format']),
+        'date'   => $date->format($element['#date_date_format'], array('format_string_type' => $element['#date_format_string_type'])),
+        'time'   => $date->format($element['#date_time_format'], array('format_string_type' => $element['#date_format_string_type'])),
         'object' => $date,
       );
     }
@@ -574,9 +575,10 @@ function datetime_datetime_validate($element, &$form_state) {
     }
     else {
       // If the date is valid, set it.
-      $date = $input['object'];
-      if ($date instanceOf DrupalDateTime && !$date->hasErrors()) {
-        form_set_value($element, $date, $form_state);
+      $date = $element['#default_value'];
+      $new_date = @$date->modify($input['date'].' '.$input['time']);
+      if ($new_date && $new_date instanceOf DrupalDateTime && !$new_date->hasErrors()) {
+        form_set_value($element, $new_date, $form_state);
       }
       // If the date is invalid, set an error. A reminder of the required
       // format in the message provides a good UX.
@@ -643,11 +645,12 @@ function datetime_html5_format($part, $element) {
  *
  */
 function datetime_format_example($format) {
+  $format_type = datetime_default_format_type();
   $date = &drupal_static(__FUNCTION__);
   if (empty($date)) {
     $date = new DrupalDateTime();
   }
-  return $date->format($format);
+  return $date->format($format, array('format_string_type' => $format_type));
 }
 
 /**