通过年月日判断星期几，但是不知道为什么switch语句没有执行

#include<stdio.h>
int main()
{
int csgo(int x,int y,int z);
int Y,m,D,N,K,P,z,Q,H,M;
printf("请输入年月日");
scanf("%d,%d,%d",&Y,&m,&D);
if((Y%4==0&&Y%100!=0)||Y%400==0)
{
switch(m)
{
case 1: M == 0 ;break;
case 2: M == 31 ;break;
case 3: M == 60 ;break;
case 4: M == 91 ;break;
case 5: M == 121 ;break;
case 6: M == 152 ;break;
case 7: M == 182 ;break;
case 8: M == 213 ;break;
case 9: M == 244 ;break;
case 10: M == 274 ;break;
case 11: M == 305 ;break;
case 12: M == 335 ;break;
}
N = (Y%4)365+(Y/4)(3653+366)-365;
K = M+N+z;
P = K%7;
switch(P)
{
case 1:Q =1 ;break;
case 2:Q= 2 ;break;
case 3:Q= 3 ;break;
case 4:Q =4 ;break;
case 5:Q =5 ;break;
case 6:Q =6 ;break;
case 0:Q =7 ;break;
}
}
else
{
switch(m)
{
case 1: M == 0 ;break;
case 2: M == 31 ;break;
case 3: M == 59 ;break;
case 4: M == 90 ;break;
case 5: M == 120 ;break;
case 6: M == 151 ;break;
case 7: M == 181 ;break;
case 8: M == 212 ;break;
case 9: M == 243 ;break;
case 10: M == 373 ;break;
case 11: M == 304 ;break;
case 12: M == 334 ;break;
}
N = (Y%4)365+(Y/4)(3653+366)-365;
int L;
L=z;
K = M+N+L;
P = K%7;
switch(P)
{
case 1:Q =1 ;break;
case 2:Q =2 ;break;
case 3:Q=3 ;break;
case 4:Q =4 ;break;
case 5:Q =5 ;break;
case 6:Q =6 ;break;
case 0:Q =7 ;break;
}
}
if((Y%4==0&&Y%100!=0||Y/400==0)&&D== 29&&M==2 )
printf("该日期不存在");
printf("这一天是星期%d\n",Q);
return 0;

是直接写

switch(M){
case:0
case:1}