function wc_timezone_string() {
	// Added in WordPress 5.3 Ref https://developer.wordpress.org/reference/functions/wp_timezone_string/.
	if ( function_exists( 'wp_timezone_string' ) ) {
		return wp_timezone_string();
	}

	// If site timezone string exists, return it.
	$timezone = get_option( 'timezone_string' );
	if ( $timezone ) {
		return $timezone;
	}

	// Get UTC offset, if it isn't set then return UTC.
	$utc_offset = floatval( get_option( 'gmt_offset', 0 ) );
	if ( ! is_numeric( $utc_offset ) || 0.0 === $utc_offset ) {
		return 'UTC';
	}

	// Adjust UTC offset from hours to seconds.
	$utc_offset = (int) ( $utc_offset * 3600 );

	// Attempt to guess the timezone string from the UTC offset.
	$timezone = timezone_name_from_abbr( '', $utc_offset );
	if ( $timezone ) {
		return $timezone;
	}

	// Last try, guess timezone string manually.
	foreach ( timezone_abbreviations_list() as $abbr ) {
		foreach ( $abbr as $city ) {
			// WordPress restrict the use of date(), since it's affected by timezone settings, but in this case is just what we need to guess the correct timezone.
			if ( (bool) date( 'I' ) === (bool) $city['dst'] && $city['timezone_id'] && intval( $city['offset'] ) === $utc_offset ) { // phpcs:ignore WordPress.DateTime.RestrictedFunctions.date_date
				return $city['timezone_id'];
			}
		}
	}

	// Fallback to UTC.
	return 'UTC';
}