Calendar will be a new core application for GNOME.
It's still very early in its development, but it's starting to look pretty nice and to be usable.
If someone wants to try it out, I made a repository with the latest Git HEAD packaged, just run the following:
# wget http://repos.fedorapeople.org/repos/bochecha/gnome-calendar/fedora-gnome-calendar.repo -O /etc/yum.repos.d/fedora-gnome-calendar.repo # yum install gnome-calendar
Ultimately, I'll push it to Fedora proper (unless someone beats me to it ;-)), but for now a side-repository will do.