function _changeDate (oDate){

		CalendarUtils._checkCalendarDate(oDate);

		var iYear = oDate.getYear();
		CalendarUtils._checkYearInValidRange(iYear);

		if (!this.getDate() || !oDate.isSame(CalendarDate.fromLocalJSDate(this.getDate(), oDate.getCalendarType()))) {
			var oCalDate = new CalendarDate(oDate);
			this.setProperty("date", oDate.toLocalJSDate());
			this._oDate = oCalDate;
		} else {
			this.invalidate();
		}
	}
@param {sap.ui.unified.calendar.CalendarDate} oDate the calendar date
@private