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From "Hayo (JIRA)" <j...@apache.org>
Subject [jira] Created: (LANG-312) DateFormatUtils.format with Timezone parameter "CET" produces wrong date in summer time 1945 to 1949
Date Thu, 04 Jan 2007 14:47:27 GMT
DateFormatUtils.format with Timezone parameter "CET" produces wrong date in summer time 1945
to 1949
----------------------------------------------------------------------------------------------------

                 Key: LANG-312
                 URL: https://issues.apache.org/jira/browse/LANG-312
             Project: Commons Lang
          Issue Type: Bug
    Affects Versions: 2.2, 2.1
         Environment: IBM Java 1.4.2, Sun Java 1.4.2, Windows XP, SuSE Linux Enterprise 9,
German systems, at winter time
            Reporter: Hayo


DateFormatUtils.format(dt, "dd/MM/yyyy", Timezone.getTimezone("CET"), Locale.GERMANY); returns
the date of the day before during summer time of the years 1945 to 1949. The problem was detected
on a system running in Locale.GERMANY, current time "CET", JDK 1.4.2.

The problem does not occur with the call DateFormatUtils.format(dt, "dd/MM/yyyy"); which presumably
uses the system defaults. These are likely to be the same as the parameters i have passed.

The following code snippet demonstrates the problem:

        for (int year = 0; year < 150; year ++) {
            for (int month = 0; month <= 11; month ++) {
                for (int day = 1; day <= 28; day ++) {
                    java.sql.Date dt = new java.sql.Date(year, month, day); // or java.util.Date
                    String def = DateFormatUtils.format(dt, "dd/MM/yyyy");
                    String cet = DateFormatUtils.format(dt, "dd/MM/yyyy", Timezone.getTimezone("CET"),
Locale.GERMANY);
                    
                    if (!cet.equals(def)) {
                        System.err.println(dt.toLocaleString() + " Default: " + def + " CET:
" + cet);
                    }
                }
            } 
        }
        
Output:
------
        
03.04.1945 00:00:00 Default: 03/04/1945 CET:02/04/1945
        [...]
18.11.1945 00:00:00 Default: 18/11/1945 CET:17/11/1945
15.04.1946 00:00:00 Default: 15/04/1946 CET:14/04/1946
        [...]
07.10.1946 00:00:00 Default: 07/10/1946 CET:06/10/1946
07.04.1947 00:00:00 Default: 07/04/1947 CET:06/04/1947
        [...]
05.10.1947 00:00:00 Default: 05/10/1947 CET:04/10/1947
19.04.1948 00:00:00 Default: 19/04/1948 CET:18/04/1948
        [...]
03.10.1948 00:00:00 Default: 03/10/1948 CET:02/10/1948
11.04.1949 00:00:00 Default: 11/04/1949 CET:10/04/1949
        [...]
02.10.1949 00:00:00 Default: 02/10/1949 CET:01/10/1949

This seems to be during the summer time of 1949 to 1945 in Berlin, and only in Berlin. Setting
the Locale to any other value has no effect on that. So i ask myself, what results other central
european users get. Setting the Timezone to "GMT+2" extracts exactly the high summer times
in 1945 and 1947 (MEHSZ). (See below for list of summer times).

I could guess that some calendar calculations work with different libraries that have different
summer time maps (java.util.Date vs. Calendar). This might depend on my environment, so this
task should be tested by others (with their local Timezone).

The API documentation does not clearly state what effect the Timezone/Locale parameters should
have.

In my strong opinion at least dates passed as java.sql.Date should not be normalized to summer/standard
time. A date is a date! For java.util.Date the date recalculation behaviour should be mentioned
in the docs, if it is really intended this way by design.

===============================================================================

These where the actual summer times in Germany 
(http://www.ptb.de/de/org/4/44/441/salt.htm 
 http://de.wikipedia.org/wiki/Hochsommerzeit#Mitteleurop.C3.A4ische_Sommerzeit)

a) Summer time, Advance to CET (GMT+1): 1 hour (GMT+2)
1916-04-30       23:00:00 CET   until     1916-10-01  1:00:00 CEST
1917-04-16        2:00:00 CET   until     1917-09-17  3:00:00 CEST
1918-04-15        2:00:00 CET   until     1918-09-16  3:00:00 CEST

1919 until 1939: No Summer time

1940-04-01        2:00:00 CET   until     1942-11-02  3:00:00 CEST
1943-03-29        2:00:00 CET   until     1943-10-04  3:00:00 CEST
1944-04-03        2:00:00 CET   until     1944-10-02  3:00:00 CEST
1945-04-02        2:00:00 CET   until     1945-09-16  2:00:00 CEST

Special: Berlin and sowjet occupied zone:
(1945-05-24)      2:00:00 CET   until     1945-11-18  3:00:00 CEST
(1945-05-24)      3:00:00 CET   until     1945-09-24  2:00:00 MEHSZ

1946-04-14        2:00:00 CET   until     1946-10-07  3:00:00 CEST
1947-04-06        3:00:00 CET   until     1947-10-05  3:00:00 CEST
1948-04-18        2:00:00 CET   until     1948-10-03  3:00:00 CEST
1949-04-10        2:00:00 CET   until     1949-10-02  3:00:00 CEST


b) High summer time, Advance to CET: 2 hours (GMT+3)
1947-05-11        3:00:00 CEST  until     1947-06-29  3:00:00 MEHSZ 

c) From 1950 to 1979 no Summer times

d) 1980 to now (most of central europe)
1980-04-06        2:00:00 CET   until     1980-09-28  3:00:00 CEST
...
ongoing until today




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