gnome-contacts shows wrong birthdays. The shown birthdays are always one day before the real birthday. Evolution shows the correct birthday. Maybe its a probelem of the correct timezone, i am not sure. I am living in germany.
Yes, this is timezone related: https://bugzilla.gnome.org/show_bug.cgi?id=659642
Should be fixed by this build: http://koji.fedoraproject.org/koji/buildinfo?buildID=265531
Should be fixed by https://admin.fedoraproject.org/updates/FEDORA-2011-12324 which is now in stable. I'm closing this bug, feel free to re-open it if you see this problem even with this update installed.