給你寫了一個程式，應該能看懂的：

#include <stdio.h>

#include <time.h>

#include <memory.h>

int main(void)

{

time_t t1;

time_t t2;

struct tm OldTime;

struct tm NewTime;

memset(&OldTime,0x0,sizeof(tm));

OldTime.tm_year = 110;// 2010 年表示為 2010 - 1900 = 110

OldTime.tm_mon = 12;

OldTime.tm_mday = 6;

memset(&NewTime,0x0,sizeof(tm));

NewTime.tm_year = 111;// 2011 年表示為 2011 - 1900 = 111

NewTime.tm_mon = 12;

NewTime.tm_mday = 6;

t1 = mktime(&NewTime); //2011-12-6

t2 = mktime(&OldTime); //2010-12-6

printf("%d",(t1-t2)/(24*3600));

return 0;

}