code: function(e) {
          var E = YAHOO.util.Event,
              KEYS = YAHOO.util.KeyListener.KEY,
              NAV = YAHOO.widget.CalendarNavigator;
  
          var value = (this.yearEl.value) ? parseInt(this.yearEl.value, 10) : null;
          if (isFinite(value)) {
              var dir = false;
              switch(E.getCharCode(e)) {
                  case KEYS.UP:
                      this.yearEl.value = value + NAV.YR_MINOR_INC;
                      dir = true;
                      break;
                  case KEYS.DOWN:
                      this.yearEl.value = Math.max(value - NAV.YR_MINOR_INC, 0);
                      dir = true;
                      break;
                  case KEYS.PAGE_UP:
                      this.yearEl.value = value + NAV.YR_MAJOR_INC;
                      dir = true;
                      break;
                  case KEYS.PAGE_DOWN:
                      this.yearEl.value = Math.max(value - NAV.YR_MAJOR_INC, 0);
                      dir = true;
                      break;
                  default:
                      break;
              }
              if (dir) {
                  E.preventDefault(e);
                  try {
                      this.yearEl.select();
                  } catch(err) {
                      // Ignore
                  }
              }
          }
      }
docs: Default Keyboard event handler to capture up/down/pgup/pgdown
  on the Navigator's year control (yearEl).
  
  @method _handleDirectionKeys
  @protected
  @param {Event} e The DOM event being handled