diff --git a/core/lib/Drupal/Core/Datetime/Element/Datelist.php b/core/lib/Drupal/Core/Datetime/Element/Datelist.php
index b92cdb2..b0a990f 100644
--- a/core/lib/Drupal/Core/Datetime/Element/Datelist.php
+++ b/core/lib/Drupal/Core/Datetime/Element/Datelist.php
@@ -75,7 +75,7 @@ public static function valueCallback(&$element, $input, FormStateInterface $form
         $timezone = !empty($element['#date_timezone']) ? $element['#date_timezone'] : NULL;
         $date = DrupalDateTime::createFromArray($input, $timezone);
         if ($date instanceOf DrupalDateTime && !$date->hasErrors()) {
-          date_increment_round($date, $increment);
+          static::incrementRound($date, $increment);
         }
       }
     }
diff --git a/core/modules/datetime/src/Tests/DateTimeFieldTest.php b/core/modules/datetime/src/Tests/DateTimeFieldTest.php
index 60637ff..43b4ad7 100644
--- a/core/modules/datetime/src/Tests/DateTimeFieldTest.php
+++ b/core/modules/datetime/src/Tests/DateTimeFieldTest.php
@@ -478,6 +478,33 @@ function testDatelistWidget() {
     $this->assertOptionSelected("edit-$field_name-0-value-day", '31', 'Correct day selected.');
     $this->assertOptionSelected("edit-$field_name-0-value-hour", '17', 'Correct hour selected.');
     $this->assertOptionSelected("edit-$field_name-0-value-minute", '15', 'Correct minute selected.');
+
+    // Test the widget for partial completion of fields.
+    entity_get_form_display($this->field->getTargetEntityTypeId(), $this->field->getTargetBundle(), 'default')
+      ->setComponent($field_name, array(
+        'type' => 'datetime_datelist',
+        'settings' => array(
+          'increment' => 1,
+          'date_order' => 'YMD',
+          'time_type' => '24',
+        ),
+      ))
+      ->save();
+    \Drupal::entityManager()->clearCachedFieldDefinitions();
+
+    // Display creation form.
+    $this->drupalGet('entity_test/add');
+
+    // Submit a partial date and ensure and error message is provided
+    $date_value = array('year' => 2012, 'month' => '', 'day' => '', 'hour' => '', 'minute' => '');
+    $edit = array();
+    foreach ($date_value as $part => $value) {
+      $edit["{$field_name}[0][value][$part]"] = $value;
+    }
+
+    $this->drupalPostForm(NULL, $edit, t('Save'));
+    $this->assertResponse(200);
+    $this->assertText('error has been found');
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php b/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
index 2592333..7bccf89 100644
--- a/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
+++ b/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
@@ -249,6 +249,24 @@ public function testDateTimezoneWithDateTimeObject() {
   }
 
   /**
+   * Tests the checkArray method.
+   *
+   * @param mixed $expected
+   *   Expected result of checkArray method
+   * @param array $date_value
+   *   Input argument for DateTimePlus::checkArray().
+   * @param string $message
+   *   Message to print on test failure.
+   *
+   * @dataProvider providerTestCheckArray
+  *
+   * @covers ::checkArray
+   */
+  public function testCheckArray($expected, $date_value) {
+    $this->assertEquals($expected, DateTimePlus::checkArray($date_value));
+  }
+
+  /**
    * Provides data for date tests.
    *
    * @return array
@@ -533,4 +551,32 @@ public function providerTestDateTimestamp() {
     );
   }
 
+  /**
+   * Data provider for testCheckArray().
+   *
+   * @return array
+   *   An array of arrays, each containing:
+   *    - 'expected' - The expected result of DateTimePlusTest::checkArray().
+   *    - 'input' - Input for DateTimePlusTest::checkArray().
+   *
+   * @see testCheckArray()
+   */
+  public function providerTestCheckArray() {
+
+    $data = array(
+      // Checks for completion of date array
+      array(FALSE, array('year' => 2013, 'month' => '', 'day' => '', 'hour' => '', 'minute' => '')),
+      array(FALSE, array('year' => 2013, 'month' => '12', 'day' => '', 'hour' => '', 'minute' => '')),
+      array(FALSE, array('year' => 2013, 'month' => '12', 'day' => '11', 'hour' => '', 'minute' => '')),
+      array(FALSE, array('year' => 2013, 'month' => '12', 'day' => '11', 'hour' => '10', 'minute' => '')),
+      array(TRUE, array('year' => 2013, 'month' => '12', 'day' => '11', 'hour' => '10', 'minute' => '09')),
+
+      // Checks for invalid time pairings
+      array(FALSE, array('year' => 2013, 'month' => '12', 'day' => '11', 'hour' => '10', 'minute' => '61')),
+      array(FALSE, array('year' => 2013, 'month' => '12', 'day' => '11', 'hour' => '25', 'minute' => '09')),
+    );
+
+    return $data;
+  }
+
 }