The swingbench tool provides a facility to format the datestamps printed out from the tool.
Submitter observed that the offset value was incorrect when the local timezone entered into a DST time period.

Sustaining comment : The parsing of the TZ variable seems to cause issue. I've reproduced with the swingbench tool but will write a more simplified testcase to debug this issue. This issue is not seen in JDK 7 or later.