请问计算星期几的程序怎么编，最简单的那种？

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    int today,after;
    char *week[7] = {"Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"};

    do
    {
        cout << "Today is week(1-7) : ";
        cin >> today;
        while (!getchar());
        if (today >= 1 && today <= 7){
            cout << "after : ";
            cin >> after;
            while (!getchar());

            int valueafter = after % 7;

            int temp = today + valueafter - 1;
            if (temp > 7){
                temp -= 7;
            }

            cout << "Today is " << week[today - 1] << ",after " << after << " days is " << week[temp] << endl;
        }
        if (0 == today){
            break;
        }
        
    } while (1);
   
    return 0;
}