if (start=end i day=yearday(i) total+=day return total Date befday( Date d int n)/*求某日期之前若干天的日期* I int i, j, day, yda int months[13]={0,31,28,31,30,31,30,31,31,30,31,30,31} months [2]=monthday(d year) for(da month=1, i=1; i<=12; i++) (da i da. montI day=day-months[i] else elseif (start==end) return abs(te-ts); else {total=0; for (i=start;i<=end;i++) { day=yearday(i); if (i==start) total+=day-ts; else if (i==end) total+=te; else total+=day; } } return total; } Date befday(Date d,int n) /*求某日期之前若干天的日期 */ { int i,j,day,yday; Date da; int months[13]={0,31,28,31,30,31,30,31,31,30,31,30,31}; months[2]=monthday(d.year); day=dayofyear(d); if (day>n) { da.year=d.year; day=day-n; for (da.month=1,i=1;i<=12;i++) if (day-months[i]>=0) { da.month++; day=day-months[i]; } else { if (day) da.day=day; else da.day=1; break; } }