下面算“今天”是第幾天。

如果要算某天，你只要輸出年月日，再調YMD_hhmmss_2_s70 得 time_t 值（代替 now) 就可以了。方法同生日轉bt.

# include

# include

time_t YMD_hhmmss_2_s70(int Y, int M, int D, int hh, int mm, int ss){

struct tm *target_tm;

time_t tt;

time (&tt);

target_tm=localtime(&tt);

target_tm->tm_year = Y - 1900;

target_tm->tm_mon= M - 1;

target_tm->tm_mday = D;

target_tm->tm_hour = hh; // hour

target_tm->tm_min = mm;

target_tm->tm_sec = ss;

tt = mktime(target_tm); // from tm to time_t (s)

return tt;

}

main()

{

int b_year,b_month,b_day;

time_t bt, now;

long double dif;

int d;

now = time(NULL);

printf("input b_year, month,day\n");

scanf("%d %d %d",&b_year,&b_month,&b_day);

bt = YMD_hhmmss_2_s70( b_year,b_month,b_day, 0, 0, 1);

dif = difftime (now,bt);

d = (int) (dif / 86400.0);

printf("days: %d\n",d);

}

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時間函式運用方法