Неправильный вывод дня недели по заданной дате

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class JavaDateTest {
public static void main(String[] args) throws IOException {
long s;
long s1;
int t;
int j;
int k;
int h;
int i;
String ye;
String mo;
String da;
 
BufferedReader stream = new BufferedReader(new InputStreamReader(System.in));
 
JavaDate kdm = new JavaDate();
 
System.out.print("\nInput the year");
ye = stream.readLine();
while  (ye.length()!=4) {
   System.out.print("Wrong value, \""+ye+"\" repeat!\nInput the year again");
   ye = stream.readLine();
  }
System.out.print(ye);
 
 
System.out.print("\nInput the month");
mo = stream.readLine();
while     (Integer.parseInt(mo)<1
        || Integer.parseInt(mo)>12) {
   System.out.print("Wrong value \""+mo+"\", repeat!\nInput the month again");
   mo = stream.readLine();
  }
System.out.print(mo);
 
        
System.out.print("\nInput the day");
da = stream.readLine();
while     (Integer.parseInt(da)<1
        || Integer.parseInt(da)>31) {
   System.out.print("Wrong value, \""+da+"\" repeat!\nInput the day again");
   da = stream.readLine();
  }
System.out.println(da);
 
char a[] = ye.toCharArray();
i = a[0] - 48;
j = a[1] - 48;
k = a[2] - 48;
h = a[3] - 48;
int y = i*1000 + j*100 + k*10 + h;
 
char b[] = new char[2];
if (mo.length()<2) {
    b[0] = 0;
    b[1] = mo.toCharArray()[0];
} else {
    b[0] = mo.toCharArray()[0];
    b[1] = mo.toCharArray()[1];
}
i = b[0] - 48;
j = b[1] - 48;
int m = i*10 + j;
 
char c[] = new char[2];
if (da.length()<2){  
    c[0] = 0;
    c[1] = da.toCharArray()[0];
} else {
    c[0] = da.toCharArray()[0];
    c[1] = da.toCharArray()[1];
}
i = b[0] - 48;
j = b[1] - 48;
int d = i*10 + j;
 
s = (y - 1 - ((y - 1) % 4))/4*366 + (y - 1 - (y - 1 - ((y - 1) % 4))/4)*365;
s1 = kdm.month(m);
s1 += d; 
s += s1;
if (y%4 == 0)
s1 = s%7;
else s1 = (s % 7) - 1;
t = (char)(s1 + 48);
j = t - 48;
kdm.date(j);
System.exit(0);
}}
 
class JavaDate {
    public int month(int m1) {
    int g;
    switch (m1) {
    case 1: {g = 0; break;}
    case 2: {g = 31;break;}
        case 3: {g = 59;break;}
    case 4: {g = 90;break;}
        case 5: {g = 120;break;}
    case 6: {g = 151;break;}
        case 7: {g = 181;break;}
    case 8: {g = 212;break;}
    case 9: {g = 243;break;}
        case 10: {g = 273;break;}
        case 11: {g = 304;break;}
        default: {g = 334;break;}
    }
    return g;
     }
    
    public void date(int o) {
    String f;
    switch (o) {
    case 1: {f = "Monday";break;}
        case 2: {f = "Tuesday";break;}
        case 3: {f = "Wednesday";break;}
        case 4: {f = "Thursday";break;}
        case 5: {f = "Friday";break;}
        case 6: {f = "Saturday";break;}
        default: {f = "Sunday";break;}
    }
   System.out.println(f);
}}