Show current timezone beside time fields.

Closes #3285427

scheduler.module

@@ -260,16 +260,23 @@ function _scheduler_entity_form_alter(&$form, FormStateInterface $form_state, $f
     $descriptions['format'] = t('Enter a date and time.');
   }
 
+  $logged_in_user_id = \Drupal::currentUser()->id();
+  $user_edit_url = "/user/$logged_in_user_id/edit";
   if (!$publishing_required) {
-    $descriptions['blank'] = t('Leave the date blank for no scheduled publishing.');
+    $descriptions['blank'] = t('Leave the date blank for no scheduled publishing. To configure your timezone, <a href="@url" target="_blank">edit your user profile</a>', [
+      '@url' => $user_edit_url,
+    ]);
   }
 
   $form['publish_on']['#access'] = $publishing_enabled && $publishing_displayed;
   $form['publish_on']['widget'][0]['value']['#required'] = $publishing_required;
   $form['publish_on']['widget'][0]['value']['#description'] = Xss::filter(implode(' ', $descriptions));
+  $form['#after_build'][] = "scheduler_append_timezone_to_fields";
 
   if (!$unpublishing_required) {
-    $descriptions['blank'] = t('Leave the date blank for no scheduled unpublishing.');
+    $descriptions['blank'] = t('Leave the date blank for no scheduled publishing. To configure your timezone, <a href="@url" target="_blank">edit your user profile</a>', [
+      '@url' => $user_edit_url,
+    ]);
   }
   else {
     unset($descriptions['blank']);
@@ -346,6 +353,27 @@ function _scheduler_entity_form_alter(&$form, FormStateInterface $form_state, $f
   }
 }
 
+/**
+ * Add timezone after 'publish on' and 'unpublish on' field in node forms.
+ *
+ * @see _scheduler_entity_form_alter()
+ */
+function scheduler_append_timezone_to_fields($form, &$form_state) {
+  $user_timezone = \Drupal::currentUser()->getTimezone();
+  $date = new DateTime('', new DateTimeZone($user_timezone));
+  $abbr_timezone = $date->format('T');
+  $user_timezone_arr = explode('/', $user_timezone);
+  $user_timezone_str = $user_timezone_arr[1] ?? '';
+  $processed_user_timezone = str_replace('_', ' ', $user_timezone_str);
+  if ($form['publish_on']) {
+    $form['publish_on']['widget'][0]['value']['time']['#suffix'] = '<div class="timezone_suffix">' . $abbr_timezone . ' (' . $processed_user_timezone . ')</div>';
+  }
+  if ($form['unpublish_on']) {
+    $form['unpublish_on']['widget'][0]['value']['time']['#suffix'] = '<div class="timezone_suffix">' . $abbr_timezone . ' (' . $processed_user_timezone . ')</div>';
+  }
+  return $form;
+}
+
 /**
  * Form alter handling for entity type forms.
  */