code: public void setCellEditorValue(Object value) {
          dateTimePicker.clear();
          if (value == null) {
              return;
          }
          if (value instanceof LocalDateTime) {
              LocalDateTime nativeValue = (LocalDateTime) value;
              dateTimePicker.setDateTimePermissive(nativeValue);
          } else {
              String text = value.toString();
              String shorterText = InternalUtilities.safeSubstring(text, 0, 100);
              dateTimePicker.datePicker.setText(shorterText);
          }
      }
docs: setCellEditorValue, This sets the picker to an appropriate value for the supplied object. If
  the value is null, then picker will be cleared. If the value is a LocalDateTime instance,
  then the picker will be set to that value. All other types (including strings) will be read
  or converted to a string with a maximum length of the first 100 characters. The date picker
  text will be set with the resulting string.