为什么用devc++是221但是用这个网站输出却是22097？？？

#include<stdio.h>

int main()

{

int year = 2008;

    int month = 8;

    int day = 8;

    int a;

    int sum;

    month--;

    for(;month>=1;month--){

switch(month)

{

                case 1:a=31; break;

case 2:a=28;

if(year%4==0&&year%100!=0){

a=29;

}

break;

case 3:a=31;break;

case 5:a=31;break;

case 7:a=31;break;

case 8: a=31;break;

case 10:a=31;break;

case 12:a=31;break;

default: a=30;break;

}

sum += a;

    }

    sum = sum + day;

    printf("%d",sum);

return 0;

}