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Date: Thu, 6 Sep 2012 01:03:05 -0700 (PDT)
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Subject: Date/Calendar confusion
From: Ulrich Scholz <d7@thispla.net>
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Xref: csiph.com comp.lang.java.programmer:18568

Dear all,

have a look at the function below (Java 5).  The first result is 0 as expected. But why is the second one different?

Thanks, Ulrich
 

private static void testDate() throws ParseException
    {
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS");
        TimeZone timeZone = TimeZone.getTimeZone("GMT");
        timeZone.setRawOffset(0); // get GMT time zone for sure
        dateFormat.setTimeZone(timeZone);

        Calendar calendar1 = Calendar.getInstance(timeZone, Locale.US);
        Date date1 = dateFormat.parse("1970-01-01T00:00:00.000");
        calendar1.setTime(date1);
        System.out.println(calendar1.getTimeInMillis()); // is 0

        Calendar calendar2 = Calendar.getInstance(timeZone, Locale.US);
        Date date2 = dateFormat.parse("0000-00-00T00:00:00.000");
        calendar2.setTime(date2);

        // adjust for the epoch 01.01.1970
        //
        calendar2.set(Calendar.YEAR, calendar2.get(Calendar.YEAR) + 1970);
        calendar2.set(Calendar.MONTH, calendar2.get(Calendar.MONTH) + 1);
        calendar2.set(Calendar.DAY_OF_MONTH, calendar2.get(Calendar.DAY_OF_MONTH) + 1);

        System.out.println(calendar2.getTimeInMillis()); // should be 0 but is -124335907200000
    }