二进制时间换算

void GetNowDate(char *datestr,char *format)
{
	time_t nnowtime = time(NULL);
	struct tm tm_nowtime = *(localtime(&nnowtime));
	datestr[0] =0;
	strftime(datestr, 30, format, &tm_nowtime);
}
int main() {

	char szNowDate[32] = {0};
	GetNowDate(szNowDate, (char *)"%Y%m%d");
   string strNowDate = szNowDate;
   string sYear = strNowDate.substr(0,4);
   string sMoth = strNowDate.substr(4,2);
   string sDay = strNowDate.substr(6,2);

	std::cout<<sYear<<std::endl;
	std::cout<<sMoth<<std::endl;
	std::cout<<sDay<<std::endl;

	int iYear = atoi(sYear.c_str());
	int iMoth = atoi(sMoth.c_str());
	int iDay = atoi(sDay.c_str());
	std::cout<<iYear<<std::endl;
	std::cout<<iMoth<<std::endl;
	std::cout<<iDay<<std::endl;

	int isYear = iYear - 2019;
	bitset<6> bs(isYear);
		//cout << bs << endl;
		string strBs = bs.to_string();

		bitset<4> bMoth(iMoth);
		string strMoth = bMoth.to_string();
		bitset<5> bDay(iDay);
		string strDay = bDay.to_string();
		std::cout<<strBs<<std::endl;
		std::cout<<strMoth<<std::endl;
		std::cout<<strDay<<std::endl;