diff --git a/web/includes/config.php.in b/web/includes/config.php.in
index 9128c2710e..54de31165f 100644
--- a/web/includes/config.php.in
+++ b/web/includes/config.php.in
@@ -146,34 +146,51 @@ $timeFormatter = new IntlDateFormatter(null, IntlDateFormatter::NONE, IntlDateFo
 require_once('database.php');
 require_once('logger.php');
 loadConfig();
-if (ZM_LOCALE_DEFAULT) {
-  try {
-    if (ZM_TIMEZONE) {
-      $dateFormatter = new IntlDateFormatter(ZM_LOCALE_DEFAULT, IntlDateFormatter::SHORT, IntlDateFormatter::NONE, ZM_TIMEZONE);
-      $dateTimeFormatter = new IntlDateFormatter(ZM_LOCALE_DEFAULT, IntlDateFormatter::SHORT, IntlDateFormatter::LONG, ZM_TIMEZONE);
-      $timeFormatter = new IntlDateFormatter(ZM_LOCALE_DEFAULT, IntlDateFormatter::NONE, IntlDateFormatter::LONG, ZM_TIMEZONE);
-    } else {
-      $dateFormatter = new IntlDateFormatter(ZM_LOCALE_DEFAULT, IntlDateFormatter::SHORT, IntlDateFormatter::NONE);
-      $dateTimeFormatter = new IntlDateFormatter(ZM_LOCALE_DEFAULT, IntlDateFormatter::SHORT, IntlDateFormatter::LONG);
-      $timeFormatter = new IntlDateFormatter(ZM_LOCALE_DEFAULT, IntlDateFormatter::NONE, IntlDateFormatter::LONG);
-    }
-  } catch(Exception $e) {
-    ZM\Error($e->getMessage());
-    $dateFormatter = new IntlDateFormatter(null, IntlDateFormatter::SHORT, IntlDateFormatter::NONE);
-    $dateTimeFormatter = new IntlDateFormatter(null, IntlDateFormatter::SHORT, IntlDateFormatter::LONG);
-    $timeFormatter = new IntlDateFormatter(null, IntlDateFormatter::NONE, IntlDateFormatter::LONG);
+ZM\Logger::fetch()->initialise();
+
+$locale = ZM_LOCALE_DEFAULT;
+$locales = ResourceBundle::getLocales('');
+if ($locale) {
+  if (!array_search($locale, $locales)) {
+    ZM\Warning("Locale $locale does not seem to be valid.");
+    $locale = locale_get_default();
   }
+} else {
+  ZM\Warning('No locale set');
+  $locale = locale_get_default();
 }
-if (ZM_DATE_FORMAT_PATTERN) {
-  $dateFormatter->setPattern(ZM_DATE_FORMAT_PATTERN);
-}
-if (ZM_DATETIME_FORMAT_PATTERN) {
-  $dateTimeFormatter->setPattern(ZM_DATETIME_FORMAT_PATTERN);
+
+try {
+  if (ZM_TIMEZONE) {
+    $dateFormatter = new IntlDateFormatter($locale, IntlDateFormatter::SHORT, IntlDateFormatter::NONE, ZM_TIMEZONE);
+    $dateTimeFormatter = new IntlDateFormatter($locale, IntlDateFormatter::SHORT, IntlDateFormatter::LONG, ZM_TIMEZONE);
+    $timeFormatter = new IntlDateFormatter($locale, IntlDateFormatter::NONE, IntlDateFormatter::LONG, ZM_TIMEZONE);
+  } else {
+    $dateFormatter = new IntlDateFormatter($locale, IntlDateFormatter::SHORT, IntlDateFormatter::NONE);
+    $dateTimeFormatter = new IntlDateFormatter($locale, IntlDateFormatter::SHORT, IntlDateFormatter::LONG);
+    $timeFormatter = new IntlDateFormatter($locale, IntlDateFormatter::NONE, IntlDateFormatter::LONG);
+  }
+} catch(Exception $e) {
+  error_log($e->getMessage());
+  $dateFormatter = new IntlDateFormatter(null, IntlDateFormatter::SHORT, IntlDateFormatter::NONE);
+  $dateTimeFormatter = new IntlDateFormatter(null, IntlDateFormatter::SHORT, IntlDateFormatter::LONG);
+  $timeFormatter = new IntlDateFormatter(null, IntlDateFormatter::NONE, IntlDateFormatter::LONG);
 }
-if (ZM_TIME_FORMAT_PATTERN) {
-  $timeFormatter->setPattern(ZM_TIME_FORMAT_PATTERN);
+
+try {
+  # PHP 8.1.26 made these throw an exception if locale is invalid so have to try
+  if (ZM_DATE_FORMAT_PATTERN) {
+    $dateFormatter->setPattern(ZM_DATE_FORMAT_PATTERN);
+  }
+  if (ZM_DATETIME_FORMAT_PATTERN) {
+    $dateTimeFormatter->setPattern(ZM_DATETIME_FORMAT_PATTERN);
+  }
+  if (ZM_TIME_FORMAT_PATTERN) {
+    $timeFormatter->setPattern(ZM_TIME_FORMAT_PATTERN);
+  }
+} catch(\Error $e) {
+  error_log($e->getMessage());
 }
-ZM\Logger::fetch()->initialise();
 
 $GLOBALS['defaultUser'] = array(
   'Username'  => 'admin',