const 
  SecPerDay = 86400; 
  SecPerHour = 3600; 
  SecPerMinute = 60; 

function SecondToTime(const Seconds: Cardinal): Double; 
var 
  ms, ss, mm, hh, dd: Cardinal; 
begin 
  dd := Seconds div SecPerDay; 
  hh := (Seconds mod SecPerDay) div SecPerHour; 
  mm := ((Seconds mod SecPerDay) mod SecPerHour) div SecPerMinute; 
  ss := ((Seconds mod SecPerDay) mod SecPerHour) mod SecPerMinute; 
  ms := 0; 
  Result := dd + EncodeTime(hh, mm, ss, ms); 
end; 

procedure TForm1.Button1Click(Sender: TObject); 
begin 
  label1.Caption := DateTimeToStr(Date + SecondToTime(86543)); 
end;