diff --git src/wp-admin/includes/schema.php src/wp-admin/includes/schema.php
index 20853da3ec..0dd63ab3f4 100644
--- src/wp-admin/includes/schema.php
+++ src/wp-admin/includes/schema.php
@@ -404,6 +404,16 @@ function populate_options( array $options = array() ) {
 	 * for all timezone strings supported by PHP.
 	 */
 	$offset_or_tz = _x( '0', 'default GMT offset or timezone string' ); // phpcs:ignore WordPress.WP.I18n.NoEmptyStrings
+
+	/**
+	 * Filters the default GMT offset or timezone string.
+	 *
+	 * @since 5.X.X
+	 *
+	 * @param string $offset_or_tz The default GMT offset or timezone string.
+	 */
+	$offset_or_tz = apply_filters( 'populate_option_timezone_string', $offset_or_tz );
+
 	if ( is_numeric( $offset_or_tz ) ) {
 		$gmt_offset = $offset_or_tz;
 	} elseif ( $offset_or_tz && in_array( $offset_or_tz, timezone_identifiers_list() ) ) {