diff -u b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
--- b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
@@ -73,16 +73,6 @@
         $this->setTimeZone($date2);
 
         $output2 = $this->formatDate($date2);
-
-        // Check if start day == end day.
-        if ($this->getFieldSetting('datetime_type') == 'datetime') {
-          // TODO better logic to split the date and time based on the format.
-          $length = strspn($output2, $output);
-          if ($length) {
-
-            $output2 = substr($output2, $length - 1);
-          }
-        }
       }
 
       // Display the date using theme datetime.
--- a/core/modules/datetime/datetime.install
+++ b/core/modules/datetime/datetime.install
@@ -13,76 +13,6 @@
  * Add 'value2' field.
  */
 function datetime_update_8001() {
-  // Update field storage for existing datetime fields.
-  $entity_manager = \Drupal::entityManager();
-  $entity_manager->useCaches(FALSE);
-  $change_list = array();
-
-  foreach ($entity_manager->getDefinitions() as $entity_type_id => $entity_type) {
-
-    if ($entity_manager->getStorage($entity_type_id) instanceof \Drupal\Core\Entity\Schema\DynamicallyFieldableEntityStorageSchemaInterface) {
-      $field_changes = array();
-
-      $storage_definitions = $entity_manager->getFieldStorageDefinitions($entity_type_id);
-      $original_storage_definitions = $entity_manager->getLastInstalledFieldStorageDefinitions($entity_type_id);
-
-      // Detect updated field storage definitions.
-      foreach (array_intersect_key($storage_definitions, $original_storage_definitions) as $field_name => $storage_definition) {
-
-        if ($storage_definition->getType() == 'datetime') {
-          if ($entity_manager->getStorage($entity_type_id)->requiresFieldStorageSchemaChanges($storage_definition, $original_storage_definitions[$field_name])) {
-            $field_changes[$field_name] = TRUE;
-          }
-        }
-      }
-
-      if ($field_changes) {
-        $change_list[$entity_type_id] = array(
-          'field_storage_definitions' => $field_changes,
-          'base_table' => $entity_type->getBaseTable(),
-          'revision_table' => $entity_type->getRevisionTable(),
-        );
-      }
-    }
-  }
-
-  $field_spec = array(
-    'description' => 'The end date value.',
-    'type' => 'varchar',
-    'length' => 20,
-  );
-
-  $schema = Database::getConnection()->schema();
-
-  foreach ($change_list as $entity_type_id => $changes) {
-    foreach (array_keys($changes['field_storage_definitions']) as $field_name) {
-      $value_field_name = $field_name . '_value2';
-
-      $field_schema = array(
-        'fields' => array(
-          $value_field_name => array(
-            'description' => 'The end date value.',
-            'type' => 'varchar',
-            'length' => 20,
-          ),
-        ),
-        'indexes' => array(
-          $value_field_name => array($value_field_name),
-        ),
-      );
-
-      $index_spec = array($value_field_name);
-      $base_table = $changes['base_table'] . '__' . $field_name;
-      $schema->addField($base_table, $value_field_name, $field_spec);
-      $schema->addIndex($base_table, $value_field_name, $index_spec, $field_schema);
-
-      if ($changes['revision_table']) {
-        $revision_table = $changes['revision_table'] . '__' . $field_name;
-        $schema->addField($revision_table, $value_field_name, $field_spec);
-        $schema->addIndex($revision_table, $value_field_name, $index_spec, $field_schema);
-      }
-    }
-  }
 
   // Update the storage configs.
   if (!$field_storage_configs = \Drupal::entityManager()->getStorage('field_storage_config')->loadByProperties(array('type' => 'datetime'))) {