code: @Override
      public void zEventCustomPopupWasClosed(CustomPopup popup) {
          popup = null;
          if (timeMenuPanel != null) {
              timeMenuPanel.clearParent();
          }
          timeMenuPanel = null;
          lastPopupCloseTime = Instant.now();
      }
docs: zEventCustomPopupWasClosed, This is called automatically whenever the CustomPopup that is
  associated with this time picker is closed. This should be called regardless of the type of
  event which caused the popup to close.
  
  Notes: The popup can be automatically closed for various reasons. 1) The user may press
  escape. 2) The popup may lose focus. 3) The window may be moved. 4) The user may toggle the
  popup menu with the "toggle time menu" button. 5) The user may select a time in the popup
  menu.