输入日期求星期的程序

/**
*  week.c
*  version:1.0 2006-9-14
*  auther:jsp
*
*  W= (d+2*m+3*(m+1)/5+y+y/4-y/100+y/400) mod 7
*  在公式中d表示日期中的日数，m表示月份数，y表示年数。
*  注意：在公式中有个与其他公式不同的地方：
*   把一月和二月看成是上一年的十三月和十四月，例：如果是2004-1-10则换算成：2003-13-10来代入公式计算。
*/
#include"stdio.h"

struct data{
 short year;
 short month;
 short day;
};

int IsLoopYear(struct data *today)
{
 if((today->year % 400 == 0)||((today->year % 100 != 0) &&(today->year % 4 == 0)))
  return 1;
 else return 0;
}

void main()
{
 struct data today,ctoday;
 short week;

 while(1)
 {
  printf("请输入今天的日期(dddd-dd-dd):");
  scanf("%d-%d-%d",&today.year ,&today.month ,&today.day);
  if(today.month ==2)
   if (IsLoopYear(&today) == 1)
    if((today.day > 29) || (today.day < 1))
    {
     printf("日期输入错误请重来!/n");
     continue;
    }
    
  if(today.month ==2)
   if (IsLoopYear(&today) == 0)
    if((today.day > 28) ||(today.day < 1))
    {
     printf("日期输入错误请重来!/n");
     continue;
    }

  if((today.month == 1) || (today.month == 3) ||(today.month == 5)||(today.month == 7)||(today.month == 8)||(today.month == 10)||(today.month == 12))
   if((today.day > 31) ||(today.day < 1))
   {
    printf("日期输入错误请重来!/n");
    continue;
   }
  if((today.month == 4) || (today.month == 6) ||(today.month == 9)||(today.month == 11))
   if((today.day > 30) ||(today.day < 1))
   {
    printf("日期输入错误请重来!/n");
    continue;
   }
  
  if((today.month >12) || (today.month < 1))
  {
   printf("月份输入错误请重来!/n");
   continue;

  }

  ctoday = today;
 if(today.month == 1 )
 {
  today.month = 13;
  today.year = today.year-1;
 }
 
 if(today.month == 2 )
 {
  today.month = 14;
  today.year = today.year-1;
 }

 week = (today.day + 2*today.month +3*(today.month  + 1)/5+today.year +today.year /4-today.year /100+today.year /400) %7;
 week ++;

 switch(week)
 {
 case 1:
  printf("%d年%d月%d日是星期一/n",ctoday.year ,ctoday.month ,ctoday.day );
  break;
 case 2:
  printf("%d年%d月%d日是星期二/n",ctoday.year ,ctoday.month ,ctoday.day );
  break;
 case 3:
  printf("%d年%d月%d日是星期三/n",ctoday.year ,ctoday.month ,ctoday.day );
  break;
 case 4:
  printf("%d年%d月%d日是星期四/n",ctoday.year ,ctoday.month ,ctoday.day );
  break;
 case 5:
  printf("%d年%d月%d日是星期五/n",ctoday.year ,ctoday.month ,ctoday.day );
  break;
 case 6:
  printf("%d年%d月%d日是星期六/n",ctoday.year ,ctoday.month ,ctoday.day );
  break;
 case 7:
  printf("%d年%d月%d日是星期天/n",ctoday.year ,ctoday.month ,ctoday.day );
  break;
 }
 }
}