仅供参考，遗漏了switch后面的{ }，“第%d天",year”中的逗号（，）误用了中文格式

#include <stdio.h>
int main()
{
    /* 定义需要计算的日期 */
    int year = 2008;
    int month = 8;
    int day = 8;
    int sum;/*sum是总天数*/
    if(year%4==0||year%400==0)
    {
        switch(month)
  {
            case 1:sum=day;break;
            case 2:sum=31+day;break;
            case 3:sum=60+day;break;
            case 4:sum=91+day;break;
            case 5:sum=121+day;break;
            case 6:sum=152+day;break;
            case 7:sum=182+day;break;
            case 8:sum=213+day;break;
            case 9:sum=244+day;break;
            case 10:sum=274+day;break;
            case 11:sum=305+day;break;
            case 12:sum=335+day;break;
   default:break;
  }
    }
    else
    {
        switch(month)
  {
            case 1:sum=day;break;
            case 2:sum=31+day;break;
            case 3:sum=61+day;break;
            case 4:sum=92+day;break;
            case 5:sum=122+day;break;
            case 6:sum=153+day;break;
            case 7:sum=183+day;break;
            case 8:sum=214+day;break;
            case 9:sum=245+day;break;
            case 10:sum=275+day;break;
            case 11:sum=306+day;break;
            case 12:sum=336+day;break;
   default:break;
  }
    }
    printf("%d年%d月%d日是该年的第%d天",year,month,day,sum);
 return 0;
}