Convert UTC string to TDatetime in Delphi

eg. var tm : string; dt : tdatetime;

tm := '2009-08-21T09:11:21Z'; dt := ?

procedure setISOtoDateTime(strDT:string); 
var 
  // Delphi settings save vars 
  ShortDF,ShortTF:string; 
  TS, DS :char; 
  // conversion vars 
  dd, tt, ddtt:TDateTime; 
begin 
  // example datetime test string in ISO format 
  strDT :='2009-07-06T01:53:23Z'; 
 
  // save Delphi settings 
  DS :=DateSeparator; 
  TS :=TimeSeparator; 
  ShortDF:=ShortDateFormat; 
  ShortTF:=ShortTimeFormat; 
 
  // set Delphi settings for string to date/time 
  DateSeparator:='-'; 
  ShortDateFormat:='yyyy-mm-dd'; 
  TimeSeparator:=':'; 
  ShortTimeFormat:='hh:mm:ss'; 
 
  // convert test string to datetime 
  try 
 
    dd :=StrToDate(Copy(strDT,1,Pos('T',strDT)-1)); 
    tt :=StrToTime(Copy(strDT,Pos('T',strDT)+1,8)); 
    ddtt := trunc(dd)+ frac(tt); 
 
  except 
    on EConvertErrordo 
      ShowMessage('Error in converting : '+ strDT); 
  end; 
 
  // restore Delphi settings 
  DateSeparator:= DS; 
  ShortDateFormat:=ShortDF; 
  TimeSeparator:= TS; 
  ShortTimeFormat:=ShortTF; 
 
  // display test string 
  ShowMessage(FormatDateTime('mm/dd/yyyy hh:mm:ss', ddtt)); 
end;

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