Box\Spout\Reader\XLSX\Helper\StyleHelper::isFormatCodeCustomDateFormat PHP Method

    protected function isFormatCodeCustomDateFormat($formatCode)
    {
        // if no associated format code or if using the default "General" format
        if ($formatCode === null || strcasecmp($formatCode, self::NUMBER_FORMAT_GENERAL) === 0) {
            return false;
        }
        return $this->isFormatCodeMatchingDateFormatPattern($formatCode);
    }