C - Date Duration Calculator

/****************************************************************
* Sornram9254 - linkedin.com/in/sornram9254         *
*                               *
* Ref 1 :   Convert from human readable date to epoch   *
*           http://goo.gl/qG3Nta            *
*                               *
* Ref 2 :   C Library - <time.h>                *
*           http://goo.gl/FCMGKl            *
****************************************************************/
#include <stdio.h>
#include <time.h>
int sDate(int year1,int mon1,int day1)
{
    //----------------------
    struct tm st;
    st.tm_year = year1-1900;
    st.tm_mon = mon1-1; // Month
    st.tm_mday = day1;  // Day
    st.tm_hour = 0;     // Hour
    st.tm_min = 0;      // Min
    st.tm_sec = 0;      // Sec
    st.tm_isdst = -1;   // Is DST on? 1 = yes, 0 = no, -1 = unknown
    //----------------------
    time_t start_t;
    start_t = mktime(&st);
    //printf("%d\r\n",start_t);
}
int eDate(int year2,int mon2,int day2)
{
    //----------------------
    struct tm et;
    et.tm_year = year2-1900;
    et.tm_mon = mon2-1; // Month
    et.tm_mday = day2;  // Day
    et.tm_hour = 0;     // Hour
    et.tm_min = 0;      // Min
    et.tm_sec = 0;      // Sec
    et.tm_isdst = -1;   // Is DST on? 1 = yes, 0 = no, -1 = unknown
    //----------------------
    time_t end_t;
    end_t = mktime(&et);
    //printf("%d",end_t);
}
int main ()
{
    int resultDays,isdst;
    int year1,mon1,day1,hour1,min1,sec1;
    int year2,mon2,day2,hour2,min2,sec2;

    printf("startDate : Year Mon Day\r\n");
    scanf("%d %d %d",&year1,&mon1,&day1);

    printf("endDate : Year Mon Day\r\n");
    scanf("%d %d %d",&year2,&mon2,&day2);

    double diff_t;

    time_t start_t;
    time_t end_t;

    start_t = sDate(year1,mon1,day1);
    end_t = eDate(year2,mon2,day2);

    diff_t = difftime(end_t, start_t);
    resultDays = diff_t / (60 * 60 * 24);   // sec min hour

    printf("%d",resultDays);
}