这个可以判断

#include <stdio.h>

int main() 

{ 

int year = 2008;

int month = 8;

int day = 8;

int sum=0;

  switch(month) {

case 1:

sum=0;

break;

case 2:

sum=31;

break;

case 3:

sum=59;

break;

case 4:

sum=90;

break;

case 5:

sum=120;

break;

case 6:

sum=151;

break;

case 7:

sum=181;

break;

case 8:sum=212;

break;

case 9:

sum=243;

break;

case 10:

sum=273;

break;

case 11:

sum=243;

break;

case 12:sum=334; break;        

  }

if ((year%4==0&&year%1000!=0)||year%400==0)

{

if (month>2)

{sum=sum+day+1;}

else

{sum=sum+day;}}

else 

{sum=sum+day;}

printf("%d年%d月%d日是该年的第%d天",year,month,day,sum);

return 0;

}