字符串转为 时间。时间差，几天，几小时，几分

const char* pszEndTime =“2021-09-10 12:00:00
		struct tm end = { 0 };
		sscanf_s(pszEndTime,"%d-%d-%d %d:%d:%d", &end.tm_year, &end.tm_mon, &end.tm_mday
			, &end.tm_hour, &end.tm_min, &end.tm_sec);
		end.tm_year -= 1900;
		end.tm_mon -= 1;
		end.tm_isdst = 0;
		time_t tEnd = mktime(&end);

		time_t tNow;
		time(&tNow); //从1970至今多少秒	
		long fDis = difftime(tEnd, tNow);
		int nDay = fDis / (24 * 60 * 60);
		int nHour = fDis % (24 * 60 * 60) / (60 * 60);
		int nMin = fDis % (24 * 60 * 60) % (60 * 60) / 60;
		int nSec = fDis % 60;
		nSec = fDis % 60;