diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/TimestampFormatter.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/TimestampFormatter.php
index a24f5dd..f73f083 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/TimestampFormatter.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/TimestampFormatter.php
@@ -132,7 +132,7 @@ public function settingsForm(array $form, FormStateInterface $form_state) {
     $elements['timezone'] = [
       '#type' => 'select',
       '#title' => $this->t('Time zone'),
-      '#options' => ['' => $this->t('- Default site/user time zone -')] + system_time_zones(FALSE),
+      '#options' => ['' => $this->t('- Default site/user time zone -')] + system_time_zones(FALSE, TRUE),
       '#default_value' => $this->getSetting('timezone'),
     ];
 
diff --git a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
index c28b7f8..540da55 100644
--- a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
+++ b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
@@ -204,7 +204,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#title' => $this->t('Default time zone'),
       // Use system timezone if set, but avoid throwing a warning in PHP >=5.4
       '#default_value' => @date_default_timezone_get(),
-      '#options' => system_time_zones(),
+      '#options' => system_time_zones(NULL, TRUE),
       '#description' => $this->t('By default, dates in this site will be displayed in the chosen time zone.'),
       '#weight' => 5,
       '#attributes' => ['class' => ['timezone-detect']],
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
index 71b9467..6dbc6ca 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
@@ -98,7 +98,7 @@ public function settingsForm(array $form, FormStateInterface $form_state) {
       '#type' => 'select',
       '#title' => $this->t('Time zone override'),
       '#description' => $this->t('The time zone selected here will always be used'),
-      '#options' => system_time_zones(TRUE),
+      '#options' => system_time_zones(TRUE, TRUE),
       '#default_value' => $this->getSetting('timezone_override'),
     ];
 
diff --git a/core/modules/system/src/Form/RegionalForm.php b/core/modules/system/src/Form/RegionalForm.php
index c365fc0..a66b26b 100644
--- a/core/modules/system/src/Form/RegionalForm.php
+++ b/core/modules/system/src/Form/RegionalForm.php
@@ -65,7 +65,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     $system_date = $this->config('system.date');
 
     // Date settings:
-    $zones = system_time_zones();
+    $zones = system_time_zones(NULL, TRUE);
 
     $form['locale'] = [
       '#type' => 'details',
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index a1a6b71..d327d4e 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -845,7 +845,7 @@ function system_user_timezone(&$form, FormStateInterface $form_state) {
     '#type' => 'select',
     '#title' => t('Time zone'),
     '#default_value' => $account->getTimezone() ? $account->getTimezone() : \Drupal::config('system.date')->get('timezone.default'),
-    '#options' => system_time_zones($account->id() != $user->id()),
+    '#options' => system_time_zones($account->id() != $user->id(), TRUE),
     '#description' => t('Select the desired local time and time zone. Dates and times throughout this site will be displayed using this time zone.'),
   ];
   $user_input = $form_state->getUserInput();
@@ -1355,10 +1355,15 @@ function system_mail($key, &$message, $params) {
 /**
  * Generate an array of time zones and their local time&date.
  *
- * @param $blank
+ * @param mixed $blank
  *   If evaluates true, prepend an empty time zone option to the array.
+ * @param bool $grouped
+ *   (optional) Whether the timezones should be grouped by region.
+ *
+ * @return array
+ *   An array or nested array containing time zones, keyed by the system name.
  */
-function system_time_zones($blank = NULL) {
+function system_time_zones($blank = NULL, $grouped = FALSE) {
   $zonelist = timezone_identifiers_list();
   $zones = $blank ? ['' => t('- None selected -')] : [];
   foreach ($zonelist as $zone) {
@@ -1371,6 +1376,27 @@ function system_time_zones($blank = NULL) {
   }
   // Sort the translated time zones alphabetically.
   asort($zones);
+  if ($grouped) {
+    $grouped_zones = [];
+    foreach ($zones as $key => $value) {
+      $split = explode('/', $value);
+      $city = array_pop($split);
+      $region = array_shift($split);
+      if (!empty($region)) {
+        $grouped_zones[$region][$key] = empty($split) ? $city : $city . ' (' . join('/', $split) . ')';
+      }
+      else {
+        $grouped_zones[$key] = $value;
+      }
+    }
+    foreach ($grouped_zones as $key => $value) {
+      if (is_array($grouped_zones[$key])) {
+        asort($grouped_zones[$key]);
+      }
+    }
+    $zones = $grouped_zones;
+  }
+
   return $zones;
 }
 
diff --git a/core/modules/system/tests/src/Kernel/Timezone/TimezoneTest.php b/core/modules/system/tests/src/Kernel/Timezone/TimezoneTest.php
new file mode 100644
index 0000000..1daa00e
--- /dev/null
+++ b/core/modules/system/tests/src/Kernel/Timezone/TimezoneTest.php
@@ -0,0 +1,64 @@
+<?php
+
+namespace Drupal\Tests\system\Kernel\Timezone;
+
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Test coverage for time zone handling.
+ *
+ * @group system
+ */
+class TimezoneTest extends KernelTestBase {
+
+  public static $modules = ['system'];
+
+  /**
+   * Tests system_time_zones().
+   */
+  public function testSystemTimeZones() {
+    // Test the default parameters for system_time_zones().
+    $result = system_time_zones();
+    $this->assertInternalType('array', $result);
+    $this->assertArrayHasKey('Africa/Dar_es_Salaam', $result);
+    $this->assertEquals('Africa/Dar es Salaam', $result['Africa/Dar_es_Salaam']);
+
+    // Tests time zone grouping.
+    $result = system_time_zones(NULL, TRUE);
+
+    // Check a two-level time zone.
+    $this->assertInternalType('array', $result);
+    $this->assertArrayHasKey('Africa', $result);
+    $this->assertArrayHasKey('Africa/Dar_es_Salaam', $result['Africa']);
+    $this->assertEquals('Dar es Salaam', $result['Africa']['Africa/Dar_es_Salaam']);
+
+    // Check a three level time zone.
+    $this->assertArrayHasKey('America', $result);
+    $this->assertArrayHasKey('America/Indiana/Indianapolis', $result['America']);
+    $this->assertEquals('Indianapolis (Indiana)', $result['America']['America/Indiana/Indianapolis']);
+
+    // Make sure grouping hasn't erroneously created an entry with just the
+    // first and second levels.
+    $this->assertArrayNotHasKey('America/Indiana', $result['America']);
+
+    // Make sure grouping hasn't duplicated an entry with just the first and
+    // third levels.
+    $this->assertArrayNotHasKey('America/Indianapolis', $result['America']);
+
+    // Make sure that a grouped item isn't duplicated at the top level of the
+    // results array.
+    $this->assertArrayNotHasKey('America/Indiana/Indianapolis', $result);
+
+    // Test that the ungrouped and grouped results have the same number of
+    // items.
+    $ungrouped_count = count(system_time_zones());
+    $grouped_result = system_time_zones(NULL, TRUE);
+    $grouped_count = 0;
+    array_walk_recursive($grouped_result, function ($grouped_count) use
+    (&$grouped_count) {
+      $grouped_count++;
+    });
+    $this->assertEquals($ungrouped_count, $grouped_count);
+  }
+
+}
diff --git a/core/modules/views/src/Plugin/views/field/Date.php b/core/modules/views/src/Plugin/views/field/Date.php
index 37455cc..3014c2f 100644
--- a/core/modules/views/src/Plugin/views/field/Date.php
+++ b/core/modules/views/src/Plugin/views/field/Date.php
@@ -119,7 +119,7 @@ public function buildOptionsForm(&$form, FormStateInterface $form_state) {
       '#type' => 'select',
       '#title' => $this->t('Timezone'),
       '#description' => $this->t('Timezone to be used for date output.'),
-      '#options' => ['' => $this->t('- Default site/user timezone -')] + system_time_zones(FALSE),
+      '#options' => ['' => $this->t('- Default site/user timezone -')] + system_time_zones(FALSE, TRUE),
       '#default_value' => $this->options['timezone'],
     ];
     foreach (array_merge(['custom'], array_keys($date_formats)) as $timezone_date_formats) {