program8-3.c

// Program to determine tomorrow`s date
// (date in US-en format: mm dd yyyy)

#include <stdio.h>
#include <stdbool.h>

struct date
{
    int month;
    int day;
    int year;
};

// main routine

int main (void)
{
    struct date today, tomorrow;
    int numberOfDays(struct date d);

    printf("Enter today's date (mm dd yyyy): ");
    scanf("%i%i%i", &today.month, &today.day, &today.year);

    if (today.day != numberOfDays(today)) {
        tomorrow.day = today.day + 1;
        tomorrow.month = today.month;
        tomorrow.year = today.year;
    } else if (today.month == 12) { // end of year
        tomorrow.day = 1;
        tomorrow.month = 1;
        tomorrow.year = today.year + 1;
    } else { // end of month
        tomorrow.day = 1;
        tomorrow.month = today.month + 1;
        tomorrow.year = today.year;
    }

    printf("Tomorrow's date is %i/%i/%.2i.\n", tomorrow.month,
        tomorrow.day, tomorrow.year % 100);

    return 0;
}

// Function: find number days in month

int numberOfDays(struct date d)
{
    int days;
    bool isLeapYear(struct date d);
    const int daysPerMonth[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30,
        31, 30, 31};

    if (isLeapYear(d) == true && d.month == 2)
        days = 29;
    else
        days = daysPerMonth[d.month - 1];

    return days;
}

// Function: determine if leap year

bool isLeapYear(struct date d)
{
    bool leapYearFlag;

    if ((d.year % 4 == 0 && d.year % 100 != 0) ||
        d.year % 400 == 0) 
        leapYearFlag = true; // It's a leap year
    else 
        leapYearFlag = false; // It's not a leap year

    return leapYearFlag;
    
}