diff --git a/core/lib/Drupal/Core/Datetime/Element/Datelist.php b/core/lib/Drupal/Core/Datetime/Element/Datelist.php
index b0a990f..b560065 100644
--- a/core/lib/Drupal/Core/Datetime/Element/Datelist.php
+++ b/core/lib/Drupal/Core/Datetime/Element/Datelist.php
@@ -55,14 +55,7 @@ public static function valueCallback(&$element, $input, FormStateInterface $form
     $date = NULL;
     if ($input !== FALSE) {
       $return = $input;
-      $filled_keys = TRUE;
-      foreach ($input as $key => $value) {
-        if (empty($value)) {
-          $filled_keys = FALSE;
-          break;
-        }
-      }
-      if ($filled_keys) {
+      if (is_null(static::checkEmptyInputs($input, $parts))) {
         if (isset($input['ampm'])) {
           if ($input['ampm'] == 'pm' && $input['hour'] < 12) {
             $input['hour'] += 12;
@@ -309,6 +302,7 @@ public static function validateDatelist(&$element, FormStateInterface $form_stat
     $input_exists = FALSE;
     $input = NestedArray::getValue($form_state->getValues(), $element['#parents'], $input_exists);
     if ($input_exists) {
+      $first_empty = static::checkEmptyInputs($input, $element['#date_part_order']);
 
       // If there's empty input and the field is not required, set it to empty.
       if (empty($input['year']) && empty($input['month']) && empty($input['day']) && !$element['#required']) {
@@ -318,6 +312,10 @@ public static function validateDatelist(&$element, FormStateInterface $form_stat
       elseif (empty($input['year']) && empty($input['month']) && empty($input['day']) && $element['#required']) {
         $form_state->setError($element, t('The %field date is required.'));
       }
+      elseif (!is_null($first_empty)) {
+        $message = t('The %field date is invalid. A value must be selected for %part.', array('%field' => !empty($element['#title']) ? $element['#title'] : '', '%part' => $first_empty));
+        $form_state->setError($element, $message);
+      }
       else {
         // If the input is valid, set it.
         $date = $input['object'];
@@ -333,6 +331,30 @@ public static function validateDatelist(&$element, FormStateInterface $form_stat
   }
 
   /**
+   * Checks the input array for empty values.
+   *
+   * Input array keys are checked against values in the parts array. Elements
+   * not in the parts array are ignored. If no empty values are found, null is
+   * returned. Otherwise, returns the first key in the input array that has an
+   * empty value.
+   *
+   * @param array $input
+   *
+   * @param array $parts
+   *
+   * @return string
+   *
+   */
+  protected static function checkEmptyInputs($input, $parts) {
+    foreach ($parts as $part) {
+      if (empty($input[$part])) {
+        return $part;
+      }
+    }
+    return null;
+  }
+
+  /**
    * Rounds minutes and seconds to nearest requested value.
    *
    * @param $date
diff --git a/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php b/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
index 7bccf89..5291fc6 100644
--- a/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
+++ b/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
@@ -255,8 +255,6 @@ public function testDateTimezoneWithDateTimeObject() {
    *   Expected result of checkArray method
    * @param array $date_value
    *   Input argument for DateTimePlus::checkArray().
-   * @param string $message
-   *   Message to print on test failure.
    *
    * @dataProvider providerTestCheckArray
   *