I've blogged about this before but I'm going to do it again.
Why, oh why do people insist on building their own TZ databases and ignoring the Operating Systems TZ dataset? Is this just a really stupid case of NIH? I've hit this in drupal (specifically the Events Module), Plone (inherited from zope), and I've been told about java having it's own tz set as well.
I might even do a t-shirt, this has got me that annoyed!