code: function (ui) {
        var start = Math.round(ui.position.top / this.periodPosition);
        var end = Math.round(($(ui.helper).height() + ui.position.top) / this.periodPosition);
  
        return this.periodFormat(start) + ' - ' + this.periodFormat(end);
      }
docs: Return a readable period string from a drag event
  @param ui
  @returns {string}