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}};

/* Sets day of year from month and day using ptrs instead of indexes */
int day_of_year(int year, int month, int day) {
  int i, leap;

  leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;

  for (i = 1; i < month; i++)
    day += *(*(daytab + leap) + i);

  return day;
}

/* Sets month and day from day of year using ptrs instead of indexes */
void month_day(int year, int yearday, int *pmonth, int *pday) {
  int i, leap;

  leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;

  for (i = 1; yearday > *(*(daytab + leap) + i); i++)
    yearday -= *(*(daytab + leap) + i);

  *pmonth = i;
  *pday = yearday;
}