获得时间秒数（从1970.01.01 00:00:00算起）

近来有不少人问这问题，所以写到这来，免得重复回答

#include <time.h>
#include <iostream>
using std::cout;

int main (int argc, char* argv[])
{
 struct tm* when = (struct tm*) malloc (sizeof (tm);

 when->tm_year = 105;//2005.07.21 22:35:23 year = cur year - 1900
 when->tm_mon = 7;
 when->tm_mday = 21;
 when->tm_hour =21;
 when->tm_min = 35;
 when->tm_sec = 23;

 t = mktime (when);
 cout << t << endl;
 return 0;
}