diff --git a/wp-admin/includes/schema.php b/wp-admin/includes/schema.php
index 5a04ce4750..504acbf949 100644
--- a/wp-admin/includes/schema.php
+++ b/wp-admin/includes/schema.php
@@ -388,13 +388,23 @@ function populate_options( array $options = array() ) {
 	/*
 	 * translators: default GMT offset or timezone string. Must be either a valid offset (-12 to 14)
 	 * or a valid timezone string (America/New_York). See https://www.php.net/manual/en/timezones.php
-	 * for all timezone strings supported by PHP.
+	 * for all timezone strings currently supported by PHP.
+	 *
+	 * Important: When a previous timezone string, like `Europe/Kiev`, has been superseded by an
+	 * updated one, like `Europe/Kyiv`, as a rule of thumb, the **old** timezone name should be used
+	 * in the "translation" to allow for the default timezone setting to be PHP cross-version compatible,
+	 * as old timezone names will be recognized in new PHP versions, while new timezone names cannot
+	 * be recognized in old PHP versions.
+	 *
+	 * To verify which timezone strings are available in the _oldest_ PHP version supported, you can
+	 * use https://3v4l.org/6YQAt#v5.6.20 and replace the "BR" (Brazil) in the code line with the
+	 * country code for which you want to look up the supported timezone names.
 	 */
 	$offset_or_tz = _x( '0', 'default GMT offset or timezone string' );
 	if ( is_numeric( $offset_or_tz ) ) {
 		$gmt_offset = $offset_or_tz;
-	} elseif ( $offset_or_tz && in_array( $offset_or_tz, timezone_identifiers_list(), true ) ) {
-			$timezone_string = $offset_or_tz;
+	} elseif ( $offset_or_tz && in_array( $offset_or_tz, timezone_identifiers_list( DateTimeZone::ALL_WITH_BC ), true ) ) {
+		$timezone_string = $offset_or_tz;
 	}
 
 	$defaults = array(
diff --git a/wp-includes/version.php b/wp-includes/version.php
index ec388a3110..e5ec50a318 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-alpha-54231';
+$wp_version = '6.1-alpha-54232';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.