code: public final void showDateTime(LocalDateTime dateTime) {
          requireNonNull(dateTime);
  
          if (!dayPage.isHidden()) {
              selectedPage.set(getDayPage());
          } else if (!weekPage.isHidden()) {
              selectedPage.set(getWeekPage());
          } else if (!monthPage.isHidden()) {
              selectedPage.set(getMonthPage());
          } else if (!yearPage.isHidden()) {
              selectedPage.set(getYearPage());
          }
  
          setDate(dateTime.toLocalDate());
          setRequestedTime(dateTime.toLocalTime());
      }
docs: Sends the request to the calendar view to display the given date and
  time. The view will switch to the {@link DayPage} and set the value of
  {@link #dateProperty()} to the date and {@link #requestedTimeProperty()}
  to the time.
  
  @param dateTime the date and time to show in the view