whymathbad.c

//
//  main.c
//  ch10
//
//  Created by john salyer on 2/12/13.
//  Copyright (c) 2013 john salyer. All rights reserved.
//

#include <stdio.h>
#include <time.h>

int main(int argc, const char * argv[])
{

    //what is now?
    
    long secondsSince1970 = time(NULL);
    
    struct tm now = *localtime(&secondsSince1970);  //the number of seconds since jan 1 1970
    
    //localtime_r(&secondsSince1970, &now);
    
    printf("The date now is %d-%d-%d\n", now.tm_mon+1, now.tm_mday, now.tm_year+1900);
    
    
    printf("days since Jan 1: %d \n",now.tm_yday+1);
    
    //what is 4M seconds from now?
    
    long fourmillion = 4000000;
    
    long plusfourmillion = secondsSince1970 + fourmillion;
    
    struct tm future;
    
    localtime_r(&plusfourmillion, &future);
    
    printf("The date in 4 million seconds will be %d-%d-%d\n", future.tm_mon+1, future.tm_mday, future.tm_year+1900);
    
    //it should be something like 46.296296296 days!!!
    
    printf("days since Jan 1: %d \n",future.tm_yday+1);
    
    //why is it 47?
    printf("What's %d - %d = %d\n",future.tm_yday+1, now.tm_yday+1, future.tm_yday - now.tm_yday );
    
    
    //shouldn't be the number of seconds that we're calculating?
    printf("Tell us the difference between NOW %li and THEN %li equals %li", secondsSince1970, plusfourmillion, secondsSince1970 - plusfourmillion);
    
    
    
    return 0;
}

why is it -9? what is so hard about long subtraction and addition?

Joey, I was reading about Time Structures.

"You can add two times by calling the AddTime function; you can subtract two times with the SubtractTime function.
All of these functions work with time structures. You can use time structures to represent either time values or durations. Time values specify a point in time, relative to a given time base. Durations specify a span of time, relative to a given time scale. Durations are represented by time structures that have the time base set to 0 (that is, the base field in the time structure is set to nil)."
Using Addtime function might solve the problem?*@?

No.