code: private void onDayClick(CalendarDay day) {
          if (mOnDayClickListener != null) {
              mOnDayClickListener.onDayClick(this, day);
          }
  
          // This is a no-op if accessibility is turned off.
          mNodeProvider.sendEventForItem(day, AccessibilityEvent.TYPE_VIEW_CLICKED);
      }
docs: Called when the user clicks on a day. Handles callbacks to the
  {@link OnDayClickListener} if one is set.
  
  @param day A time object representing the day that was clicked