function _handleOpen() {
		this.addStyleClass(InputBase.ICON_PRESSED_CSS_CLASS);
		this._renderedDays = this._getCalendar().$("-Month0-days").find(".sapUiCalItem").length;

		InstanceManager.addPopoverInstance(this._oPopup);

		this._oCalendar.focus();
		this.fireAfterValueHelpOpen();
	}
Adds or extracts a given number of measuring units from the "dateValue" property value

@param {int} iNumber to use for increasing the dateValue
@param {string} sUnit for day, month or year