C program to find the number of days between two given dates

Write a C program to find the number of days between two given dates.

  #include <stdio.h>

  int daysInMonth[] = {31, 28, 31, 30, 31, 30,
                               31, 31, 30, 31, 30, 31};

  /* given year is leap year or not */
  int isLeapYear(int year) {
        int flag = 0;
        if (year % 100 == 0) {
                if (year % 400 == 0) {
                        flag = 1;
                } else {
                        flag = 0;
                }
        } else if (year % 4 == 0) {
                flag = 1;
        }
        return flag;
  }

  int main() {

        int year, month, date, days = 0, i;

        int cyear, cmonth, cdate, tmpMon, tmpYear;

        char str[100];

        /* get From date from the user */

        printf("From date(dd:mon:year):\n");

        fgets(str, 100, stdin);

        sscanf(str, "%d:%d:%d", &date, &month, &year);

        /* get To date from the user */

        printf("To date(dd:mon:year):\n");

        fgets(str, 100, stdin);

        sscanf(str, "%d:%d:%d", &cdate, &cmonth, &cyear);

        tmpMon = month;

        tmpYear = year;

        /* if From & To date are from same month and year */

        if (cyear == year && cmonth == month) {

                days = cdate - date + 1;

                printf("No of days: %d\n", days);

                return 0;

        }

        /* From month is feb - add additional 1 day if leap year */

        if (month == 2) {

                days = daysInMonth[month - 1] - date + 1 + isLeapYear(year);

        } else {

                days = daysInMonth[month - 1] - date + 1;

        }

        /* From month is feb - move forward to next year and month to Jan */

        if (month == 12) {

                month = 0;

                year++;

        }

        while (year <= cyear) {

                for (i = month; i < 12; i++) {

                        if ((year == cyear) && (i == cmonth - 1)) {

                                /* To date's month and year */

                                days = days + cdate;

                                break;

                        }

                        if (i == 1) {

                                /* leap year validation for feb month */

                                days = days + daysInMonth[i] + isLeapYear(year);

                        } else {

                                days = days + daysInMonth[i];

                        }

                }

                month = 0;

                year++;

        }

        /* print the results */

        printf("No of days from %02d:%02d:%d to %02d:%02d:%d is %d\n",

                date, tmpMon, tmpYear, cdate, cmonth, cyear, days);

        return 0;

  }

  Output:

  jp@jp-VirtualBox:~/$ ./a.out
  From date(dd:mon:year):
  13:12:1991
  To date(dd:mon:year):
  23:06:2013
  No of days from 13:12:1991 to 23:06:2013 is 7864