code: public void setCurrentDate(@Nullable CalendarDay day, boolean useSmoothScroll) {
      if (day == null) {
        return;
      }
      int index = adapter.getIndexForDay(day);
      pager.setCurrentItem(index, useSmoothScroll);
      updateUi();
    }
docs: Set the calendar to a specific month or week based on a date.
  
  In month mode, the calendar will be set to the corresponding month.
  
  In week mode, the calendar will be set to the corresponding week.
  
  @param day a CalendarDay to focus the calendar on. Null will do nothing
  @param useSmoothScroll use smooth scroll when changing months.