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;
}

}