Calendar Generator in C

               It is a classic concept in mathematics. Calendar has a day, month and year. It also deals with leap year which comes 4 year once.

Let us create a calendar generator based on year.

C implementation:

It uses 4 functions to implement this concept.

• LeapYear_check() : Used to check the given year is leap or not.
• getDays_Month() : This gives you number of days in a month.
• Get_firstDay() : It gives the first day of the month using Zeller’s Congruence.
• Display_month() : displays the month of the calendar.

Finally, main() function reads the year from the user.

C Program:

#include <stdio.h>

// Check the leap year

int LeapYear_check(int year1) {

    return (year1 % 4 == 0 && year1 % 100 != 0) || (year1 % 400 == 0);

}

// Get the number of days in a month

int getDays_Month(int month1, int year1) {

    int days1[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

    if (month1 == 2 && LeapYear_check(year1)) return 29;

    return days1[month1 - 1];

}

// Find the weekday of the first day of a month using Zeller’s Congruence

int get_firstday(int day1, int month1, int year1) {

    if (month1 < 3) {

        month1 += 12;

        year1--;

    }

    int k = year1 % 100;

    int j = year1 / 100;

    int weekday1 = (day1 + 13*(month1 + 1)/5 + k + k/4 + j/4 + 5*j) % 7;

    return (weekday1 + 6) % 7; // sometimes make Sunday = 0

}

// Display the calendar for a month

void display_Month(int month1, int year1) {

    char *months1[] = {

        "January", "February", "March", "April", "May", "June","July", "August", "September", "October", "November", "December" };

    printf("\n  ------------%s-------------\n", months1[month1 - 1]);

    printf("  Sun Mon Tue Wed Thu Fri Sat\n");

    int days1 = getDays_Month(month1, year1);

    int start_Day = get_firstday(1, month1, year1);

    for (int i = 0; i < start_Day; i++) {

        printf("    ");

    }

    for (int day1 = 1; day1 <= days1; day1++) {

        printf("%4d", day1);

        if ((day1 + start_Day) % 7 == 0) printf("\n");

    }

    printf("\n");

}

// Main function

int main() {

    int year1;

    printf("Enter year: ");

    scanf("%d", &year1);

 

    for (int month1 = 1; month1 <= 12; month1++) {

        display_Month(month1, year1);

    }

    return 0;

}

Output:

This output is sample one for 2 months. But this program gives you entire year.

Hope, you understood the concept and the program implementation. Keep Coding!!!!