c语言日期转化的问题

程序要求：
把某年某月某天这种日期形式转换为某年中第几天的表示形式，反之亦然。下列两个例子实现日期转换，前一个中函数day_of_year将某年某月某日转化为某年中的第几天。而第二个例子则相反。
eg1:

#include <stdio.h>
#include <stdlib.h>
static char  daydtab[2][13]={{0,31,28,31,30,31,30,31,31,30,31,30,31},
                           {0,31,29,31,30,31,30,31,31,30,31,30,31}
};

int main()
{
    int  year, month,day;
    int  days;

    printf("please input year:mouth:day\n");
    scanf("%d:%d:%d",&year,&month,&day);
    days=day_of_year(year,month,day);
    printf("%d\n",days);
    return 0;

}
int day_of_year(int  year,int  month,int  day)
{
    int leap;
    int i;

    if(year%4==0 && year %100!=0 || year %400==0)
        leap=1;
    if(month<1||month>12)
    {
        printf("your input month error");
        return -1;

    }
    if(day<1 || day>daydtab[leap][month])
    {
        printf("your input day  error");
        return -1;

    }
       for(i = 1; i < month; i++)
       day = day + daydtab[leap][i];

       return day;
}

eg2:

#include <stdio.h>
static char daytab[2][13]={
    {0,31,28,31,30,31,30,31,31,30,31,30,31},
    {0,31,29,31,30,31,30,31,31,30,31,30,31}
};

int main()
{

    //int *day="0";
    int yearday;
    int year;

    printf("please input year:day:\n");
    scanf("%d:%d",&year,&yearday);
    month_day(year,yearday,0,0);
    return 0;
}

void month_day(int year,int yearday,int *pmonth,int *pday)
{
    int i;
    int leap;


   leap = year%4==0 && year%100 !=0 || year%400==0;
   for(i=1;i<12 && yearday>daytab[leap][i];i++)
       yearday-=daytab[leap][i];

   if(i>12 && yearday>daytab[leap][12])
   {
       *pmonth=-1;
       *pday=-1;


   }
   else
   {
       *pmonth=i;
       *pday=yearday;
       return ;
   }


}

其中第二个例子出现段错误，求高手赐教指点。