Use VarToDateTime instead. It supports many more date formats in the string and converts them automatically.
var
DateVal: TDateTime;
begin
DateVal := VarToDateTime('23 Sep 2010');
ShowMessage(DateToStr(DateVal));
end;
I see you’re using Delphi 5. Some versions of Delphi will need to add Variants to the uses clause; most later versions add it for you. I don’t remember which category Delphi 5 fell into.