输入一日期,求该日期是该年中的第几天?

用该日期直接减这一年的开始日期1月1号.
var date1,date2,Dstart,Dend,Dcount:Tdatetime;
    Dstart:=strtodate('2008-1-1');
    Dend:=date();
    Dcount:=Dend-Dstart;
    edit1.text:=floattostr(Dcount);

procedure TForm1.Button2Click(Sender: TObject);
var
    year1: string;
    year2: integer;
    month1: string;
    month2: integer;
    mont: integer;
    days2: integer;
    days4: integer;
    days1: string;
    days3: integer;
    i: integer;
    mont1,mont2,mont3 : set of 01..12;
begin
mont1:=[01,03,05,07,08,10,12];
mont2:=[04,06,09,11];
mont3:=[02];
days2:=0;
year1:=LeftStr(edit2.Text,4);
month1:=MidStr(edit2.Text,6,2);
days1:=RightStr(edit2.Text,2);
year2:= StrToInt(year1);
month2:=StrToInt(month1);
days3:= StrToInt(days1);
mont:=month2;
for i:= 1 to mont-1 do
begin
   if i in mont1 then  days4:=31
   else
       if  i in mont2  then   days4:=30
       else
           if  i in mont3  then
                 if IsLeapYear(year2)=true then  days4:=29
                else  days4:=28;
    days2:=days2+days4;
end;
  days2:=days2+days3;
  edit3.Text:=edit2.Text;
  edit4.Text:=IntToStr(days2);
end;