cvs

Check out the portage repo:

cvs -d :pserver:anonymous@anoncvs.gentoo.org/var/cvsroot co gentoo-x86

Check out a repo using a specific date:

cvs -d :pserver:anonymous@anoncvs.gentoo.org:/var/cvsroot co -D "Mon Dec 1 09:14:20 2014 UTC" gentoo-x86

Check out a directory and date from a repo:

cvs -d :pserver:anonymous@anoncvs.gentoo.org:/var/cvsroot co -D "Tue Nov 11 08:33:36 2014 UTC" gentoo-x86/net-misc/curl