蔡勒公式 根据年月日计算星期几的代码

private int zellerWeek(int year,int month,int day){
   int m = month;
   int d= day;
   if(month <= 2){
      year--;
      m=month+12;
   }
   int y = year%100;
   int c = year/100;

   int w = (y+y/4+c/4-2*c+(13*(m+1)/5)+d-1)%7;
   if(w<0)
      w+=7;
   return w;
}