const char * uuiddate (unsigned long long s){
    int z = s / 86400 + 719468;
    int era = (z >= 0 ? z : z - 146096) / 146097;
    unsigned doe = static_cast<unsigned>(z - era * 146097);
    unsigned yoe = (doe - doe/1460 + doe/36524 - doe/146096) / 365;
    int y = static_cast<int>(yoe) + era * 400;
    unsigned doy = doe - (365*yoe + yoe/4 - yoe/100);
    unsigned mp = (5*doy + 2)/153;
    unsigned d = doy - (153*mp+2)/5 + 1;
    unsigned m = mp + (mp < 10 ? 3 : -9);
    y += (m <= 2);
    std::string month = std::to_string(m);
	std::string day = std::to_string(d);
	std::string year = std::to_string(y);
	std::string output = year + '-' + month + '-' + day;
	const char * c = output.c_str();
	return c;
}