public function addToForm()
 {
     global $lng;
     if ($this->getForm() instanceof ilPropertyFormGUI) {
         // :TODO: use DateDurationInputGUI ?!
         if (!(bool) $this->text_input) {
             $check = new ilCheckboxInputGUI($this->getTitle(), $this->addToElementId("tgl"));
             $check->setValue(1);
             $checked = false;
         } else {
             $check = new ilCustomInputGUI($this->getTitle());
         }
         $date_from = new ilDateTimeInputGUI($lng->txt('from'), $this->addToElementId("lower"));
         $date_from->setShowTime(true);
         $check->addSubItem($date_from);
         if ($this->getLowerADT()->getDate() && !$this->getLowerADT()->isNull()) {
             $date_from->setDate($this->getLowerADT()->getDate());
             $checked = true;
         }
         $date_until = new ilDateTimeInputGUI($lng->txt('until'), $this->addToElementId("upper"));
         $date_until->setShowTime(true);
         $check->addSubItem($date_until);
         if ($this->getUpperADT()->getDate() && !$this->getUpperADT()->isNull()) {
             $date_until->setDate($this->getUpperADT()->getDate());
             $checked = true;
         }
         if (!(bool) $this->text_input) {
             $check->setChecked($checked);
         } else {
             $date_from->setMode(ilDateTimeInputGUI::MODE_INPUT);
             $date_until->setMode(ilDateTimeInputGUI::MODE_INPUT);
         }
         $this->addToParentElement($check);
     } else {
         // see ilTable2GUI::addFilterItemByMetaType()
         include_once "./Services/Form/classes/class.ilCombinationInputGUI.php";
         include_once "./Services/Form/classes/class.ilDateTimeInputGUI.php";
         $item = new ilCombinationInputGUI($this->getTitle(), $this->getElementId());
         $lower = new ilDateTimeInputGUI("", $this->addToElementId("lower"));
         $lower->setShowTime(true);
         $item->addCombinationItem("lower", $lower, $lng->txt("from"));
         if ($this->getLowerADT()->getDate() && !$this->getLowerADT()->isNull()) {
             $lower->setDate($this->getLowerADT()->getDate());
         }
         $upper = new ilDateTimeInputGUI("", $this->addToElementId("upper"));
         $upper->setShowTime(true);
         $item->addCombinationItem("upper", $upper, $lng->txt("to"));
         if ($this->getUpperADT()->getDate() && !$this->getUpperADT()->isNull()) {
             $upper->setDate($this->getUpperADT()->getDate());
         }
         $item->setComparisonMode(ilCombinationInputGUI::COMPARISON_ASCENDING);
         $item->setMode(ilDateTimeInputGUI::MODE_INPUT);
         $this->addToParentElement($item);
     }
 }