public String[] getDownloadSN(){
		String[] result = null;
		if(sncalendars!=null && sncalendars.keySet().size()>0){
			result = new String[sncalendars.keySet().size()];
		}
		else return null;
		int index=0;
		for(String sn: sncalendars.keySet()){
			if(sncalendars.get(sn)!=null && sncalendars.get(sn)[1]!=null)
				result[index++] = sn;
		}
		return result.length>0 ? result : null;
	}