Some people may find the back-quotes visually confusing, here is another option:
$ dump -0Lauf - /var | bzip2 > /home/var.dump-$(date "+%Y.%d.%m").bz2
In this case, anything inside $(..) is executed.
EDIT: My sincere apologies, I forgot I was on the FreeBSD board.. the above will not work in csh.