i yday=yearday (i) months [2]=monthday (i) f (da I for(da month=12, j=12; j>=1; j-) y-months [j da. month-- I if (day) ths [da month break Date aftday( Date d,intn)/*计算某日期之后若干天的日期*/ 1, J, day, yday int months[13]={0,31,28,31,30,31,30,31,31,30,31,30,31} months [2]=monthday(d year)else { day=n-day; for (da.year=d.year-1,i=d.year-1;i>0;i--) { yday=yearday(i); months[2]=monthday(i); if (day-yday>0) { da.year--; day=day-yday; } else { for (da.month=12,j=12;j>=1;j--) if (day-months[j]>=0) { day=day-months[j]; da.month--; } else { if (day) da.day=months[da.month]-day; else da.day=months[da.month]; break; } break; } } } return da; } Date aftday(Date d,int n) /*计算某日期之后若干天的日期*/ { int i,j,day,yday; Date da; int months[13]={0,31,28,31,30,31,30,31,31,30,31,30,31}; yday=yearday(d.year); months[2]=monthday(d.year); day=dayofyear(d); if (day+n<=yday) { da.year=d.year; day=n;