Zeller's Congruence algorithm | Find the Day for a Date.

h = (day + (13 * (month + 1)) / 5 + yearOfCentury + yearOfCentury / 4 + century / 4 + 5 * century) % 7

• h is the calculated day of the week (0 - Saturday, 1 - Sunday, ..., 6 - Friday).

• day is the day of the month (1 to 31).

• month is the month of the year (3 to 14, with January and February adjusted as 13 and 14 respectively).

• year is the year (e.g., 2023).

• century is the century part of the year (e.g., 20 for the year 2023).

• yearOfCentury is the year within the century (e.g., 23 for the year 2023).

//C++ Program Find the Day for a Date
#include <iostream>
using namespace std;

int getDayOfWeek(int day, int month, int year) {
    if (month == 1 || month == 2) {
        month += 12;
        year--;
    }

    int century = year / 100;
    int yearOfCentury = year % 100;

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

    return h;
}

int main() {
    int day, month, year;

    cout << "Enter the date (DD MM YYYY): ";
    cin >> day >> month >> year;

    int dayOfWeek = getDayOfWeek(day, month, year);

    switch (dayOfWeek) {
        case 0:
            cout << "Saturday\n";
            break;
        case 1:
            cout << "Sunday\n";
            break;
        case 2:
            cout << "Monday\n";
            break;
        case 3:
            cout << "Tuesday\n";
            break;
        case 4:
            cout << "Wednesday\n";
            break;
        case 5:
            cout << "Thursday\n";
            break;
        case 6:
            cout << "Friday\n";
            break;
        default:
            cout << "Invalid day of the week\n";
            break;
    }

    return 0;
}

Enter the date (DD MM YYYY): 12 06 2023
Monday