输出那一天是星期几

/*今天是2013 年4 月4 日星期四，编写程序，输入今天开始到12 月31 日之间的任
意日期，输出那一天是星期几。*/

#include <stdio.h>

int main(){
    int today_m,today_d,today_w;
    int month, day, result;
    int i,j,k,sum;
    int list[] = {0,31,28,31,30,31,30,31,31,30,31,30,31};

    today_m = 4;
    today_d = 4;
    today_w = 4;
    printf("Please input month,day:\n");
    do{
        scanf("%d,%d",&month,&day);
        if((month >0 && month <= 12) && day <= list[month])
            break;
        else 
            printf("error input !\n");
    }while(1);
    
    sum = 0;
    if(month >= 4){
        for(i = today_m; i < month; i++)
            sum += list[i];
        sum = sum + day - today_d;
        result = (sum + today_w) % 7;
    } else if(month < 4){
        for(i = month; i < today_m; i++)
            sum +=list[i];
        sum = sum + today_d - day;
        result = (sum - today_w) % 7;
    }

    switch(result){
    case 0: printf("sunday\n"); break;
    case 1: printf("monday\n"); break;
    case 2: printf("tuseday\n"); break;
    case 3: printf("Wednesday\n"); break;
    case 4: printf("Thursday\n"); break;
    case 5: printf("Friday\n"); break;
    case 6: printf("Saturday\n"); break;
    default: break;
    }


    

}