关于GregorianCalendar时区的有关问题？

TimeZone estZone = TimeZone.getTimeZone("EST");        SimpleDateFormat sdfEST = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");        sdfEST.setTimeZone(estZone);        Calendar calendar = Calendar.getInstance();        calendar.setTimeZone(estZone);        calendar.setTime(sdfEST.parse("2010-10-11 12:13:14"));        System.out.println(sdfEST.format(calendar.getTime()));                Calendar cal = new GregorianCalendar();        cal.set(Calendar.YEAR, calendar.get(Calendar.YEAR));        cal.set(Calendar.MONTH, calendar.get(Calendar.MONTH));        cal.set(Calendar.DAY_OF_MONTH, calendar.get(Calendar.DAY_OF_MONTH));        cal.set(Calendar.HOUR, calendar.get(Calendar.HOUR));        cal.set(Calendar.MINUTE, calendar.get(Calendar.MINUTE));        cal.set(Calendar.SECOND, calendar.get(Calendar.SECOND));        System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(cal.getTime()));