function _open(oDomRef){
		this._createPopup();

		this._createPopupContent();

		// set displayFormatType as PrimaryCalendarType
		// not only one because it depends on DataBinding
		var sCalendarType;
		var oBinding = this.getBinding("value");

		if (oBinding && oBinding.oType && oBinding.oType.oOutputFormat) {
			sCalendarType = oBinding.oType.oOutputFormat.oFormatOptions.calendarType;
		} else if (oBinding && oBinding.oType && oBinding.oType.oFormat) {
			sCalendarType = oBinding.oType.oFormat.oFormatOptions.calendarType;
		}

		if (!sCalendarType) {
			sCalendarType = this.getDisplayFormatType();
		}

		if (sCalendarType) {
			this._getCalendar().setPrimaryCalendarType(sCalendarType);
		}

		var sValue = this._bValid ? this._formatValue(this.getDateValue()) : this.getValue();
		if (sValue != this._$input.val()) {
			this.onChange(); // to check manually typed in text
		}

		this._fillDateRange();

		this._openPopup(oDomRef);

		// Fire navigate event when the calendar popup opens
		this.fireNavigate({
			dateRange: this._getVisibleDatesRange(this._getCalendar()),
			afterPopupOpened: true
		});

	}
Sets the associated legend.

@since 1.38.5
@param {sap.ui.core.ID | sap.ui.unified.CalendarLegend} oLegend ID of an element which becomes the new target of this <code>legend</code> association;
                                                        alternatively, an element instance may be given
@returns {this} Reference to <code>this</code> for method chaining
@public