Java SimpleDateFormat Bug?

Question

Does anyone know why I get the output below? I expected 2012-12 instead of 2013-12

Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR,2012);
cal.set(Calendar.MONTH,12-1);
cal.set(Calendar.DATE,30);
Date date=cal.getTime();
System.out.println(date);

String YYYY_MM=format.format(date);
System.out.println(YYYY_MM);

OUTPUT

Sun Dec 30 18:30:52 KST 2012
2013-12

EXPECTED

Sun Dec 30 18:30:52 KST 2012
2012-12

Answer 1

You are using incorrect date formatter. You can try this way,

    Calendar cal=Calendar.getInstance();
    cal.set(Calendar.YEAR,2012);
    cal.set(Calendar.MONTH,12-1);
    cal.set(Calendar.DATE,30);
    Date date=cal.getTime();
    System.out.println(date);
    SimpleDateFormat format=new SimpleDateFormat("yyyy-MM");
    // Java SimpleDateFormat use `yyyy` (lowercase) not `YYYY`(uppercase)
    String YYYY_MM=format.format(date);
    System.out.println(YYYY_MM); //out put 2012-12

Out put for me

Sun Dec 30 15:20:08 IST 2012
2012-12