控制 datetimepicker 顯示位置

1. datetimepicker 位置  pickerPosition  有以下幾個屬性值，望文生義不解釋

 $('.form_datetime').datetimepicker({
      pickerPosition: 'botom-left',
      pickerPosition: 'bottom-right',
      pickerPosition: 'top-left',
      pickerPosition: 'top-right'
  });