程序代码：

#include<stdio.h>
int week(int,int);
int main()
    {
    int year;
    scanf("%d",&year);
    for(int i=1; i<13; i++)
        if(week(year,i)==5)
            printf("%d年%d月13日是黑色星期五\n",year,i);//注某月的１３日是星期五称为黑色星期五． 
    return 0;
    }
int week(int year,int month)
    {
    if(month<3)
        {
        month+=12;
        year--;
        }
    return (13+2*month+3*(month+1)/5+year+year/4-year/100+year/400)%7+1;
    }

[此贴子已经被作者于2018-6-6 23:40编辑过]

程序代码：

#include "stdio.h"
void CaculateWeekDay(int y,int m, int d)
{
   if(m==1||m==2) {
   m+=12;
   y--;
}
int iWeek=(d+2*m+3*(m+1)/5+y+y/4-y/100+y/400)%7;
switch(iWeek)
  {
   case 0: printf("星期一\n"); break;
   case 1: printf("星期二\n"); break;
   case 2: printf("星期三\n"); break;
   case 3: printf("星期四\n"); break;
   case 4: printf("星期五\n"); break;
   case 5: printf("星期六\n"); break;
   case 6: printf("星期日\n"); break;
  }
} 
int main()
{
  int year=0,month=0,day=0;
  printf("请输入日期：\n格式为：1900,1,1\n");
  char temp = '1';
  while (temp != '0')
   {
     scanf("%d,%d,%d",&year,&month,&day);
     scanf("%c",&temp);
     CaculateWeekDay(year,month,day);
     printf("输入0退出,其他继续:");
     scanf("%c",&temp);
   }
}