求日期差

例如,我想算一下現在(2016.11.21)到明年高考(2017.6.7)還有多少天

#include<iostream>    
#include <ctime>  

using namespace std;  

int main() {  
    struct tm t1 = { 0 };  
    struct tm t2 = { 0 };  
    double seconds;  

    t1.tm_year = 2016 - 1900; t1.tm_mon = 10; t1.tm_mday = 21;//現在時間2016,11,21  
    t2.tm_year = 2017
 
 - 1900; t2.tm_mon = 5; t2.tm_mday = 7;//高考時間2017,6,7  

    seconds = difftime(mktime(&t2), mktime(&t1));//轉換結構體為time_t,利用difftime,計算時間差  

    cout << seconds / 86400 << endl;//最後輸出時間,因為一天有86400秒(60*60*24)  
    system("pause");  
    return 0;  
}