#162 DST change differs from JDK for Asia/Tehran for all years

[zubin kavarana]

Background: I am migrating an enterprise application using java.util.Date and java.sql.Date to joda-time DateTime. When unit testing in various timezones for equivalence of Joda functions to JDK there is a difference in Asia/Tehran zone.

Problem: The following methods are equivalent for most timezones tested after modern timezone was introduced

private Date addDaysToDateJoda(Date date, int days) {
Chronology chrono = GregorianChronology.getInstance();//hard set for test case simplicity
DateTimeZone dtz = DateTimeZone.forTimeZone(TimeZone.getDefault());
DateTime jodaDateTime = new DateTime(System.currentTimeMillis()).withChronology(chrono).withZone(dtz).withMillis(date.getTime());
return new Date(jodaDateTime.plusDays(days).getMillis());
}

private Date addDaysToDateJDK(Date date, int days) {
Calendar cal1 = new GregorianCalendar();
cal1.setTime(new Date(date.getTime()));
cal1.add(Calendar.DAY_OF_MONTH, days);
return new Date(cal1.getTime().getTime());
}

The Iran timezone (+3hr 30min) failed for all years whenever DST changes back to normal time offset in September/October.

1. It fails when DST ends for any year (in October (1980) and September (1991 onwards)) and into the future
2. I have used IBM J9 v2.6, JDK 1.5_22, JDK 1.6_35 and jrockit-jdk-1.6.0_33R28 for my tests, each time the JDKs are equivalent in functionality
3. All JDKs and Joda were updated to 2012d tzdata at least - the last change in the tzdata for this zone was in 2007
4. For each test run the machine timezone was also adjusted to the Asia/Tehran zone
5. I read from the FAQ that DST will be different for JDK and Joda before the modern timezones were put in effect, however the code fails for all years after 1991 and into the future
6. Changing the code to return 'new Date(jodaDateTime.plusDays(days).withLaterOffsetAtOverlap().getMillis());' makes the test case pass

[zubin kavarana]

JUnit Test Case