function _showYearPicker(){

		var oDate = this._getFocusedDate();
		var oYearPicker = this.getAggregation("yearPicker");

		this.setProperty("_currentPicker", CURRENT_PICKERS.YEAR_PICKER);

		this._showOverlay();

		oYearPicker.setDate(oDate.toLocalJSDate());

		_togglePrevNexYearPicker.call(this);
		this._iMode = 1;
	}
Opens the year picker.
This function assumes its called when a yearPicker aggregation is available, so the caller must take care for it.
@private
@returns {void}