Re: returns wrong date during DST changes in "Europe/Paris" timezone

From:

Nigel Wade <nmw@ion.le.ac.uk>

Newsgroups:

comp.lang.java.help

Date:

Tue, 12 May 2009 13:40:29 +0100

Message-ID:

<gubqnt$kf2$1@south.jnrs.ja.net>

Nadh wrote:

System clock is set to "Europe/Paris" timezone. Creating a Calendar
object with the following details gives me wrong date.

public class TimeTest
{
public static void main(String[] args) throws Exception
{
Calendar ca = new GregorianCalendar( 2009,2,29,2,0,0);
System.out.println( "March DST : " + ca.getTime());
}
}

Expected output : Sun Mar 29 02:00:00 CEST/CST 2009

Actual output : Sun Mar 29 03:00:00 CEST/CST 2009

Unfortunately it is your expectations which are incorrect, Java is returning the
correct date/time. The time you requested never actually existed, there is a
hole in the space/time continuum at that instant. The clocks went from 01:59:59
CET to 03:00:00 CEST so requesting 02:00:00 29/03/2009 CEST makes no sense, I
presume Java sets the clock to the nearest possible valid time.

Exactly the same happens at 01:00:00 in the Europe/London timezone (we change at
the same instant as central Europe, so it's one hour earlier in wallclock time)
so here 01:00:00-01:59:59 BST disappear into a discontinuity in the fabric of
time.

import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.TimeZone;

public class DSTChange {
    public static void main(String[] args) {
        TimeZone.setDefault(TimeZone.getTimeZone("Europe/Paris"));
        Calendar ca = new GregorianCalendar( );
        ca.set(2009,2,29,1,59,59);
        System.out.println( "March before DST : " + ca.getTime());
        ca.set(2009,2,29,2,0,0);
        System.out.println( "March magic DST : " + ca.getTime());
        ca.set(2009,2,29,3,0,0);
        System.out.println( "March normal DST : " + ca.getTime());

        TimeZone.setDefault(TimeZone.getTimeZone("Europe/London"));
        ca = new GregorianCalendar();
        ca.set(2009,2,29,0,59,59);
        System.out.println( "March before DST : " + ca.getTime());
        ca.set(2009,2,29,1,0,0);
        System.out.println( "March magic DST : " + ca.getTime());
        ca.set(2009,2,29,2,0,0);
        System.out.println( "March normal DST : " + ca.getTime());
    }
}

Output:
March before DST : Sun Mar 29 01:59:59 CET 2009
March magic DST : Sun Mar 29 03:00:00 CEST 2009
March normal DST : Sun Mar 29 03:00:00 CEST 2009
March before DST : Sun Mar 29 00:59:59 GMT 2009
March magic DST : Sun Mar 29 02:00:00 BST 2009
March normal DST : Sun Mar 29 02:00:00 BST 2009

--
Nigel Wade