年月日输入正确的判断与转换格式，第三章第36题

#include<stdio.h>
int printdate(int year,int month,int day)
{

switch(month)
{
case 1:
{
if((day>31)||(day<0))
printf("不合理\n");
else
printf("January %d, %d\n",day,year);
}
break;
case 2:
{
if((year%4 == 0&&year%100 != 0)||(year%400 == 0))
{
if((day>29)||(day<0))
printf("不合理\n");
else
printf("February %d, %d\n",day,year);
}
else
{
if((day>28)||(day<0))
printf("不合理\n");
else
printf("February %d, %d\n",day,year);
}
}
break;
case 3:
{
if((day>31)||(day<0))
printf("不合理\n");
else
printf("March %d, %d\n",day,year);
}
break;
case 4:
{
if(day>30)
printf("不合理\n");
else
printf("April %d, %d\n",day,year);
}
break;
case 5:
{
if((day>31)||(day<0))
printf("不合理\n");
else
printf("May %d, %d\n",day,year);
}
break;
case 6:
{
if(day>30)
printf("不合理\n");
else
printf("June %d, %d\n",day,year);
}
break;
case 7:
{
if((day>31)||(day<0))
printf("不合理\n");
else
printf("July %d, %d\n",day,year);
}
break;
case 8:
{
if((day>31)||(day<0))
printf("不合理\n");
else
printf("August %d, %d\n",day,year);
}
break;
case 9:
{
if(day>30)
printf("不合理\n");
else
printf("September %d, %d\n",day,year);
}
break;
case 10:
{
if((day>31)||(day<0))
printf("不合理\n");
else
printf("October %d, %d\n",day,year);
}
break;
case 11:
{
if(day>30)
printf("不合理\n");
else
printf("November %d, %d\n",day,year);
}
break;
case 12:
{
if((day>31)||(day<0))
printf("不合理\n");
else
printf("December %d, %d\n",day,year);
}
break;
}
return year,month,day;
}
int main()
{
int a,b,c;
while(1)
{
printf("请输入年月日");
scanf("%d %d %d",&a,&b,&c);
printdate(a,b,c);
}
return 0;
}