#include<iostream>
#include<iomanip>
using namespace std;
int type(int m) {
    if (m % 4 != 0 || (m % 100 == 0 && m % 400 != 0)) {
        return 0;//不是閏年
    }
    else{   
        return 1;//是閏年
    }
}
char week[7][10] = { "Saturday","Sunday","Monday","Tuesday","Wednesday","Thursday","Friday" };
int year[2] = { 365,366 };
int month[2][12] = { {31,28,31,30,31,30,31,31,30,31,30,31},{31,29,31,30,31,30,31,31,30,31,30,31} };
int main()
{
    int days, dayOfWeek;
    int i = 0, j = 0;
    while (cin >> days && days != -1) {//這也行？！
        dayOfWeek = days % 7;
        for (i = 2000; days >= year[type(i)]; i++) {
            days -= year[type(i)];
        }
        for (j = 0; days >= month[type(i)][j]; j++) {//很巧妙
            days -= month[type(i)][j];
        }
        cout<< i << "-"  << setw(2) << setfill('0') <<j + 1 << "-" << setw(2) << setfill('0') << days + 1 <<" "<<week[dayOfWeek] << endl;

    }
    system("pause");
}

這里的格式輸出挺容易錯(cuò)的，
要月和日都能補(bǔ)0.