protected function formatGedcomYear(): string
    {
        if ($this->year < 0) {
            return sprintf('%04d B.C.', -$this->year);
        }

        if ($this->new_old_style) {
            return sprintf('%04d/%02d', $this->year - 1, $this->year % 100);
        }

        return sprintf('%04d', $this->year);
    }