#include "stdio.h"
#include "conio.h"
struct
{int year;
int month;
int day;
}date;
main()
{int days;
printf("input year,month,day:");
scanf("%d,%d,%d",&date.year,&date.month,&date.day);
switch(date.month)
{case1:days=date.day;      break;
 case2:days=date.day+31;   break;
 case3:days=date.day+59;   break;
 case4:days=date.day+90;   break;
 case5:days=date.day+120;  break;
 case6:days=date.day+151;  break;
 case7:days=date.day+181;  break;
 case8:days=date.day+212;  break;
 case9:days=date.day+243;  break;
 case10:days=date.day+273; break;
 case11:days=date.day+304; break;
 case12:days=date.day+334; break;
}
 if((date.year%4==0&&date.year%100!=0||date.year%400==0)&&date.month>=3)
 days+=1;
 printf("\n%d/%dis the %dth day in %d.",date.month,date.day,days,date.year);
    getch();
}
要求计算日期是一年中的哪一天。结果不对，帮忙看看，谢谢。

case 和常量之间要有空格。

用了结构体一定是学过数组了，数组更简洁。
#include "stdio.h"
#include "conio.h"

struct
{
    int year;
    int month;
    int day;
}date;

main()
{
    int days,i,monthdays[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};

    printf("input year,month,day:");
    scanf("%d,%d,%d",&date.year,&date.month,&date.day);

    days=date.day;

    for(i=1;i<date.month;i++)
        days+=monthdays[i];

    if((date.year%4==0&&date.year%100!=0||date.year%400==0)&&date.month>=3)
    days++;

    printf("\n%d/%dis the %dth day in %d.\n",date.month,date.day,days,date.year);
    getch();
}

你 这 可能 写 错了
 if(date.year %4==0&&date.year%100!=0||date.year%400==0)&&(date.moth>=3)
 days+=1

moth少写了个n  不好意思啊