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From "Dan Collens (JIRA)" <>
Subject [jira] [Created] (LANG-818) FastDateFormat's "z" pattern does not respect timezone of Calendar instances passed to format()
Date Thu, 06 Sep 2012 17:49:07 GMT
Dan Collens created LANG-818:

             Summary: FastDateFormat's "z" pattern does not respect timezone of Calendar instances
passed to format()
                 Key: LANG-818
             Project: Commons Lang
          Issue Type: Bug
          Components: lang.time.*
    Affects Versions: 3.x
            Reporter: Dan Collens

The work on LANG-462 has introduced a time zone formatting bug in FastDateFormat in commons-lang3.

The problem can be seen by this snippet:
// Always prints timezone name of machine's default timezone, ignoring TZ
// set on calendar, even though the printed time itself respects calendar's TZ.
Calendar myCal = Calendar.getInstance(TimeZone.getTimeZone("US/Central"));
System.out.println(FastDateFormat.getInstance("h:mma z").format(myCal));

If you happen to be in US/Central, this will print the right thing, but just try it with US/Eastern,
US/Pacific, etc.  It will print the time in the correct timezone, but the timezone name at
the end (the "z" pattern) will always be the system default timezone.  This is a regression
against commons-lang 2.x.

Basically, when the "forced time zone" code was removed, the TimeZoneNameRule class stopped
respecting the Calendar instance's timezone, and instead now always uses the mTimeZone of
the FastDateFormat instance itself (which is only supposed to be used when formatting timezone-less
objects such as Date or long).

The removal of the forced time zone stuff is surely the right thing to do (it was a mess).
 I think the fix is to change the TimeZoneNameRule inner class to not take a TimeZone instance,
but rather to use the TimeZone on the Calendar instance passed into appendTo(), just like
TimeZoneNumberRule does.  Presumably then for efficiency, one would use the getTimeZoneDisplay()
package-static method to quickly retrieve the required timezone's display name.

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