/* static array used by both functions */
static int day_tab[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}
};
 
/* calculates the Julian day given year, month and day */
int md2j(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 += day_tab[leap][i];
 return(day);
}
 
/* calculates the month and day given year and Julian day */
j2md(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 > day_tab[leap][i]; i++)
  yearday -= day_tab[leap][i];
 *pmonth = i;
 *pday = yearday;
}