Been fooling with Zope3 on my FreeBSD box off and on for a while - but started having trouble with the unittests failing with some kind of time-related problem. Seems the results of Python's mktime() were off by an hour.
Another Zope3+FreeBSD user on the mailing wasn't seeing the problem, turns out he's in the US/Eastern timezone while I'm in US/Central. US/Mountain and US/Pacific seem OK too...it's when you're set to US/Central that it's whacked.
I was able to come up with some simple snippets of Perl and C code that seem to demonstrate the problem - which rules out it being a Python thing - and submitted a FreeBSD PR. I hope someone else can confirm this so I know I'm not losing my mind :)