Java calculate difference between months

public int monthcalculation(){
Date date = new Date();

Calendar startCalendar = new GregorianCalendar();
startCalendar.setTime(date);
System.out.println(startCalendar.get(Calendar.MONTH));
Calendar endCalendar = new GregorianCalendar();
endCalendar.set(2017,Calendar.AUGUST, 30);
System.out.println(endCalendar.get(Calendar.MONTH));
int diffYear = endCalendar.get(Calendar.YEAR) - startCalendar.get(Calendar.YEAR);
int diffMonth = diffYear * 12 + endCalendar.get(Calendar.MONTH) - startCalendar.get(Calendar.MONTH);

System.out.println("Difference of year is " + diffYear);
System.out.println("Difference is " + (diffMonth ));
return diffMonth;
}