public function getAbbreviatedName($dst = false)
    {
        $name = $this->getName();

        foreach ($this->listAbbreviations() as $abbreviation => $zones) {
            foreach ($zones as $zone) {
                if ($zone['timezone_id'] === $name && $zone['dst'] == $dst) {
                    return $abbreviation;
                }
            }
        }

        return 'unknown';
    }