See: http://www.redhat.com/archives/fedora-devel-list/2007-December/msg01764.html Change was approved on 2007-12-29 and took effect on 2007-12-31.
tzdata is once again wrong for argentina. It push an hour forward last sunday when this should happen the third sunday of October.
I can confirm this really annoying bug. Debian has already fixed it: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=501169
This bug should be closed as the upstream tzdata corrected this problem.
Right, this is a leftover.