It's test bug.
test suite: regression suite for 6u11b02
test: java/util/TimeZone/Bug6329116.java
fails with:


----------System.err:(621/52756)----------
America/Eirunepe: expected: ACT: got: AMT for non-DST in ja_JP locale.
America/Eirunepe: expected: ACT: got: AMT for non-DST in es_PE locale.
America/Eirunepe: expected: ACT: got: AMT for non-DST in en locale.
...
for all locales.

It happens because it test data (displayname.txt) we have
$ cat ../6u11b02/test/java/util/TimeZone/displayname.txt |grep America/Rio
America/Rio_Branco ACT

But in java we have AMT

Name of timezone in java is truth because:
Standard Time Zone was changed in Brazil in June 2008:

Background info: Brazil Abolishes Its Fourth Time Zone in 2008
Seconds before and after the change:
Local time DST? UTC offset Zone name
Monday, June 23, 2008 at 11:59:57 PM No -5 hours ACT
Monday, June 23, 2008 at 11:59:58 PM No -5 hours ACT
Monday, June 23, 2008 at 11:59:59 PM No -5 hours ACT
Tuesday, June 24, 2008 at 1:00:00 AM No -4 hours AMT
Tuesday, June 24, 2008 at 1:00:01 AM No -4 hours AMT
Tuesday, June 24, 2008 at 1:00:02 AM No -4 hours AMT

The background is:

http://www.timeanddate.com/news/time/brazil-abolishes-fourth-time-zone.html

So we should change ACT to AMT for America/Rio Branco in displayname.txt for all suites and tests with timezones