关于时间合法化的检验

Question

procedure TForm1.Button1Click(Sender: TObject);var
sql1:string;
sql2:string;
time:string;
ss:tdatetime;
beginif (edit1.text='') then showmessage('对不起，姓名不能为空！')
else begin
with query1 do
query1.Close;
query1.SQL.Clear;
sql2:='select * from tongxunlu where name='''+edit1.Text+'''';
query1.SQL.Add(sql2);
query1.Open;
if  not query1.Eof then begin
showmessage('对不起，该同学资料已经存在！');
edit1.Clear;
end
else begin
time:=edit3.text+'-'+combobox3.Items[combobox3.Itemindex]+'-'+combobox4.Items[combobox4.Itemindex];
query1.Close;
query1.SQL.Clear;
sql1:='insert into tongxunlu(name,sex,phone,call,adress,homeadress,email,qq,mobilephone,birthday) values(:name,:sex,:phone,:call,:adress,:homeadress,:email,:qq,:mobilephone,:birthday)';
query1.SQL.Add(sql1);
query1.ParamByName('name').AsString:=edit1.Text;
query1.ParamByName('sex').AsString:=combobox1.Items[comboBox1.ItemIndex];
query1.ParamByName('birthday').Asdatetime:=strtodatetime(time);
query1.ParamByName('phone').AsString:=edit4.Text;
query1.ParamByName('email').AsString:=edit5.Text;
query1.ParamByName('qq').AsString:=edit6.Text;
query1.ParamByName('homeadress').AsString:=edit7.Text;
query1.ParamByName('adress').AsString:=edit8.Text;
query1.ParamByName('mobilephone').AsString:=edit9.Text;
query1.ParamByName('call').AsString:=edit10.Text;
query1.ExecSQL;
 showmessage('资料添加完毕！');end ;
 end;
end;
请问，我怎么样在这个程序里加点东西，以检验时间strtodatetime是否合法，谢谢