Re: Date/Calendar confusion

From:

"John B. Matthews" <nospam@nospam.invalid>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 06 Sep 2012 20:53:48 -0400

Message-ID:

<nospam-D06BA0.20534806092012@news.aioe.org>

In article <3a69eb4a-f3c0-4b56-9a67-6833ccb2a1c8@googlegroups.com>,
Ulrich Scholz <d7@thispla.net> wrote:

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);

Note that Calendar.JANUARY is not 1. Use clear() to set some or all
fields to a known (undefined, !isSet()) state.

public static void main(String[] args) {
    TimeZone timeZone = TimeZone.getTimeZone("GMT");
    SimpleDateFormat f = new SimpleDateFormat(
        "yyyy-MMM-dd HH:mm:ss.SSS Z");

    Calendar calendar1 = Calendar.getInstance(timeZone);
    System.out.println(f.format(calendar1.getTime()));
    calendar1.clear();
    System.out.println(calendar1.getTimeInMillis()); // 0

    Calendar calendar2 = Calendar.getInstance(timeZone);
    System.out.println(f.format(calendar2.getTime()));
    calendar2.set(Calendar.YEAR, 1970);
    calendar2.set(Calendar.MONTH, Calendar.JANUARY);
    calendar2.set(Calendar.DAY_OF_MONTH, 1);
    calendar2.clear(Calendar.HOUR);
    calendar2.clear(Calendar.MINUTE);
    calendar2.clear(Calendar.SECOND);
    calendar2.clear(Calendar.MILLISECOND);
    System.out.println(calendar2.getTimeInMillis()); // 0
}

--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>