private function calculateAge(int $age): string
    {
        if ((int) ($age / 365.25) > 0) {
            $result = (int) ($age / 365.25) . 'y';
        } elseif ((int) ($age / 30.4375) > 0) {
            $result = (int) ($age / 30.4375) . 'm';
        } else {
            $result = $age . 'd';
        }

        return FunctionsDate::getAgeAtEvent($result);
    }