#include <time.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
/* 86400 seconds per day */
#define DAY 86400      

/* 
   lose the
   th, nd, st suffixes if they exist 
*/
char *remove_th_nd_st(const char *src)
{
	const char *values[3]={{"th "}, {"nd "},{"st "} };
	char *dest=strdup(src);
	char *p=NULL;
	int i=0;
	
	while(i<3)
	{
		if( (p=strstr(src,values[i++]))==NULL ) continue;
		if( !isdigit(*(p-1)) ) continue;
		p+=3;
		sprintf(dest,"%d %s",atoi(src),p); 
		break;
	}
	return dest;
}
 
/* return time difference in days 
   date1 = recent date
   date1 = older date
   ---otherwise you get a negative value which may be okay.
*/   
int date_diff(const char *date1, const char *date2)
{
    int retval=0;
    const char *fmt="%d %b %Y";
    struct tm now, then;
    char *wdate1=remove_th_nd_st(date1);
    char *wdate2=remove_th_nd_st(date2);       
    
    if ( strptime(wdate1,fmt,&now)==NULL ||
        strptime(wdate2,fmt,&then)==NULL )
    {
    	perror("Bad date format");
    	exit(EXIT_FAILURE);
    }
    now.tm_isdst = -1;  /* force mktime to get daylight savings */
    then.tm_isdst = -1;
    retval=difftime(mktime(&now),mktime(&then));
    retval=retval/DAY;
    free(wdate1);
    free(wdate2);
    return retval;
}

int main()
{
    char now[32]={0x0};
    char then[32]={0x0};
	strcpy(then,"14th June 1983");
    strcpy(now,"15th April 2006");
    printf("Date difference in days: %s - %s = %d\n",
         now,then,date_diff(now,then) );
    strcpy(now,"1st June 2005");     
    printf("Date difference in days: %s - %s = %d\n",
         now,then,date_diff(now,then) );
    strcpy(now,"2nd August 2014");
    printf("Date difference in days: %s - %s = %d\n",
         now,then,date_diff(now,then) );
    strcpy(now,"1st July 1975");
    printf("Date difference in days: %s - %s = %d\n",
         now,then,date_diff(now,then) );             
    return 0;     
}