diff --git a/core/modules/datetime/datetime.install b/core/modules/datetime/datetime.install
new file mode 100644
index 0000000..b87b230
--- /dev/null
+++ b/core/modules/datetime/datetime.install
@@ -0,0 +1,92 @@
+<?php
+
+/**
+ * @file
+ * Contains update functions for the Datetime module.
+ */
+
+/**
+ * Update datetime fields to explicitly store UTC timezone.
+ */
+function datetime_update_8601(&$sandbox) {
+  // Update field storage for existing datetime fields.
+  $entity_manager = \Drupal::entityManager();
+  $entity_manager->useCaches(FALSE);
+  $change_list = [];
+
+  foreach ($entity_manager->getDefinitions() as $entity_type_id => $entity_type) {
+    if ($entity_manager->getStorage($entity_type_id) instanceof \Drupal\Core\Entity\Schema\DynamicallyFieldableEntityStorageSchemaInterface) {
+      $field_changes = [];
+
+      $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] = [
+          'field_storage_definitions' => $field_changes,
+          'base_table' => $entity_type->getBaseTable(),
+          'revision_table' => $entity_type->getRevisionTable(),
+        ];
+      }
+    }
+  }
+
+  $field_spec = [
+    'description' => 'The date value.',
+    'type' => 'varchar',
+    'length' => 25,
+  ];
+
+  $schema = \Drupal::database()->schema();
+
+  foreach ($change_list as $entity_type_id => $changes) {
+    foreach (array_keys($changes['field_storage_definitions']) as $field_name) {
+      $value_field_name = $field_name . '_value';
+
+      $base_table = $changes['base_table'] . '__' . $field_name;
+      $schema->changeField($base_table, $value_field_name, $value_field_name, $field_spec);
+
+      $results = \Drupal::database()->query('SELECT * FROM ' . $base_table)->fetchAll();
+      foreach ($results as &$result) {
+        Drupal::database()
+          ->update($base_table)
+          ->fields([$value_field_name => $result->{$value_field_name} . '+00:00'])
+          ->condition('bundle', $result->bundle)
+          ->condition('deleted', $result->deleted)
+          ->condition('entity_id', $result->entity_id)
+          ->condition('revision_id', $result->revision_id)
+          ->condition('langcode', $result->langcode)
+          ->condition('delta', $result->delta)
+          ->execute();
+      }
+
+      if ($changes['revision_table']) {
+        $revision_table = $changes['revision_table'] . '__' . $field_name;
+        $schema->changeField($revision_table, $value_field_name, $value_field_name, $field_spec);
+
+        $results = \Drupal::database()->query('SELECT * FROM ' . $revision_table)->fetchAll();
+        foreach ($results as &$result) {
+          Drupal::database()
+            ->update($revision_table)
+            ->fields([$value_field_name => $result->{$value_field_name} . '+00:00'])
+            ->condition('bundle', $result->bundle)
+            ->condition('deleted', $result->deleted)
+            ->condition('entity_id', $result->entity_id)
+            ->condition('revision_id', $result->revision_id)
+            ->condition('langcode', $result->langcode)
+            ->condition('delta', $result->delta)
+            ->execute();
+        }
+      }
+    }
+  }
+}
diff --git a/core/modules/datetime_range/datetime_range.install b/core/modules/datetime_range/datetime_range.install
new file mode 100644
index 0000000..c9b91ff
--- /dev/null
+++ b/core/modules/datetime_range/datetime_range.install
@@ -0,0 +1,106 @@
+<?php
+
+/**
+ * @file
+ * Contains update functions for the Datetime Rage module.
+ */
+
+/**
+ * Update datetime fields to explicitly store UTC timezone.
+ */
+function datetime_range__update_8601(&$sandbox) {
+  // Update field storage for existing datetime fields.
+  $entity_manager = \Drupal::entityManager();
+  $entity_manager->useCaches(FALSE);
+  $change_list = [];
+
+  foreach ($entity_manager->getDefinitions() as $entity_type_id => $entity_type) {
+    if ($entity_manager->getStorage($entity_type_id) instanceof \Drupal\Core\Entity\Schema\DynamicallyFieldableEntityStorageSchemaInterface) {
+      $field_changes = [];
+
+      $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() === 'daterange') {
+          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] = [
+          'field_storage_definitions' => $field_changes,
+          'base_table' => $entity_type->getBaseTable(),
+          'revision_table' => $entity_type->getRevisionTable(),
+        ];
+      }
+    }
+  }
+
+  $field_spec = [
+    'description' => 'The start date value.',
+    'type' => 'varchar',
+    'length' => 25,
+  ];
+
+  $end_field_spec = [
+    'description' => 'The end date value.',
+    'type' => 'varchar',
+    'length' => 25,
+  ];
+
+  $schema = \Drupal::database()->schema();
+
+  foreach ($change_list as $entity_type_id => $changes) {
+    foreach (array_keys($changes['field_storage_definitions']) as $field_name) {
+      $value_field_name = $field_name . '_value';
+      $end_value_field_name = $field_name . 'end_value';
+
+      $base_table = $changes['base_table'] . '__' . $field_name;
+      $schema->changeField($base_table, $value_field_name, $value_field_name, $field_spec);
+      $schema->changeField($base_table, $end_value_field_name, $end_value_field_name, $end_field_spec);
+
+      $results = \Drupal::database()->query('SELECT * FROM ' . $base_table)->fetchAll();
+      foreach ($results as &$result) {
+        Drupal::database()
+          ->update($base_table)
+          ->fields([
+            $value_field_name => $result->{$value_field_name} . '+00:00',
+            $end_value_field_name => $result->{$value_field_name} . '+00:00',
+          ])
+          ->condition('bundle', $result->bundle)
+          ->condition('deleted', $result->deleted)
+          ->condition('entity_id', $result->entity_id)
+          ->condition('revision_id', $result->revision_id)
+          ->condition('langcode', $result->langcode)
+          ->condition('delta', $result->delta)
+          ->execute();
+      }
+
+      if ($changes['revision_table']) {
+        $revision_table = $changes['revision_table'] . '__' . $field_name;
+        $schema->changeField($revision_table, $value_field_name, $value_field_name, $field_spec);
+
+        $results = \Drupal::database()->query('SELECT * FROM ' . $revision_table)->fetchAll();
+        foreach ($results as &$result) {
+          Drupal::database()
+            ->update($revision_table)
+            ->fields([
+              $value_field_name => $result->{$value_field_name} . '+00:00',
+              $end_value_field_name => $result->{$value_field_name} . '+00:00',
+            ])
+            ->condition('bundle', $result->bundle)
+            ->condition('deleted', $result->deleted)
+            ->condition('entity_id', $result->entity_id)
+            ->condition('revision_id', $result->revision_id)
+            ->condition('langcode', $result->langcode)
+            ->condition('delta', $result->delta)
+            ->execute();
+        }
+      }
+    }
+  }
+}