function _getStartDate(){

		if (!this._oStartDate) {
			// no start date set, use focused date
			this._oStartDate = this._getFocusedDate();
			this._oStartDate.setDate(1); // always use begin of month
		}

		return this._oStartDate;

	}
Retrieves the start date as calendar date
@returns {sap.ui.unified.calendar.CalendarDate} the start date
@private