public Date nextTimePeriod(){
		String c = sdf.format(periodStartDate);
		int month = Integer.parseInt(c.substring(5,7));
		int day = Integer.parseInt(c.substring(8,10));
		int year = Integer.parseInt(c.substring(0,4));
		
		if(day == 1){
			day = 16;
		}else{
			day = 1;
			month++;
			if(month > 12){
				month %= 12;
				year++;
			}
		}
		String extraZeroForMonth = "0";
		String extraZeroForDay = "0";
		
		if(month > 9){
			extraZeroForMonth = "";
		}
		if(day > 9){
			extraZeroForDay = "";
		}
		String newDate = year + "-" + extraZeroForMonth + month + "-" + 
				extraZeroForDay + day;
		try{
			periodStartDate = sdf.parse(newDate);
		}catch(Exception ex){
			System.out.println(ex);
		}
		return periodStartDate;
	}