C++ program to display the calendar

               This blog creates a c++program to display the calendar. It prints a month calendar.

How to implement the program?

• First, include the built-in header files and namespace std.
• Next, check the leap year of the year.
• It checks the year is divided by 4,100 and 400, then it is leap year.
• Function daysOfMonth() assigns each month’s days value.
• For February month,check for leap year and assign the value as 29.
• Zeller’s Congruence is used to find the weekday.
• Finally, main() function gets the input as month and year and prints the calendar.

Code:

#include <iostream>

#include <iomanip>

using namespace std;

// leap year checking function

bool checkLeap(int yr) {

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

}

// days of the month

int daysOfMonth(int yr, int month) {

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

    if (month == 2 && checkLeap(yr)) return 29;

    return days[month - 1];

}

// Function to find the weekday using Zeller’s Congruence. Let us consider Sunday as 0.

int week_Day(int yr, int month, int day) {

    if (month < 3) { month += 12; yr--; }

    int K = yr % 100;

    int J = yr / 100;

    int h = (day + (13*(month+1))/5 + K + K/4 + J/4 + 5*J) % 7;

    return (h + 6) % 7; // here Sunday is assigned as 0

}

 int main() {

    int yr, month;

    cout << "Enter year and month (e.g.1 2026): ";

    cin >> month >> yr;

    cout << "\n   Calendar for " << month << "/" << yr << "\n";

    cout << "Sun Mon Tue Wed Thu Fri Sat\n";

    int fDay = week_Day(yr, month, 1);

    int tDays = daysOfMonth(yr, month);

    // Print the leading spaces

    for (int i = 0; i < fDay; i++) cout << "    ";

    // Print the days

    for (int d = 1; d <= tDays; d++) {

        cout << setw(3) << d << " ";

        if ((d + fDay) % 7 == 0) cout << "\n";

    }

    cout << "\n";

    return 0;

}

Output:

Enter year and month (e.g.1 2026): 9 2026

   Calendar for 9/2026

Sun Mon Tue Wed Thu Fri Sat

                     1     2     3     4     5

     6      7     8     9    10   11  12

    13   14   15   16   17   18  19

   20   21   22   23   24   25  26

   27   28   29   30

That’s all. The c++ program to display the calendar of year and month. Hope, this code is useful to you. Keep coding!!!