time.h是否允许Le年C

Question

I am looking for a way to find the difference between two dates. The solution needs to take into account leap years. Please see the two blocks of code below. 2012 was a leap year whereas 2013 was not, and so I fail to understand why both programs output "32 days difference". Surely they should be different if time.h does indeed take into account leap years?

The first:

#include <stdio.h>  
#include <time.h>       
int main ()
{
  struct tm start_date;
  struct tm end_date;
  time_t start_time, end_time;
  double days;

  start_date.tm_hour = 0;  start_date.tm_min = 0;  start_date.tm_sec = 0;
  start_date.tm_mon = 2; start_date.tm_mday = 1; start_date.tm_year = 112;

  end_date.tm_hour = 0;  end_date.tm_min = 0;  end_date.tm_sec = 0;
  end_date.tm_mon = 3; end_date.tm_mday = 1; end_date.tm_year = 112;

  start_time = mktime(&start_date);
  end_time = mktime(&end_date);

  days = difftime(end_time, start_time) / 86400;

  printf ("%.f days difference\n", days);

  return 0;
}

The second:

#include <stdio.h>  
#include <time.h>       
int main ()
{
  struct tm start_date;
  struct tm end_date;
  time_t start_time, end_time;
  double days;

  start_date.tm_hour = 0;  start_date.tm_min = 0;  start_date.tm_sec = 0;
  start_date.tm_mon = 2; start_date.tm_mday = 1; start_date.tm_year = 113;

  end_date.tm_hour = 0;  end_date.tm_min = 0;  end_date.tm_sec = 0;
  end_date.tm_mon = 3; end_date.tm_mday = 1; end_date.tm_year = 113;

  start_time = mktime(&start_date);
  end_time = mktime(&end_date);

  days = difftime(end_time, start_time) / 86400;

  printf ("%.f days difference\n", days);

  return 0;
}

Answer 1

Buddy just try the following (change your month as 1 and 2 respectively instead of 2 and 3, it will give you correct results, this change is tested).

As per Joachim and Floris, Month is zero based for tm_mon member, and you were counting the difference between March 1 and April 1 instead of Feb 1 and Mar 1.

  start_date.tm_hour = 0;  start_date.tm_min = 0;  start_date.tm_sec = 0;
  start_date.tm_mon = 1; start_date.tm_mday = 1; start_date.tm_year = 112;

  end_date.tm_hour = 0;  end_date.tm_min = 0;  end_date.tm_sec = 0;
  end_date.tm_mon = 2; end_date.tm_mday = 1; end_date.tm_year = 112;