Unfortunately ownCloud is not available in Debian wheezy. Even if it was promised to provide a package via backports, this seems never to happen.
As I don't like the idea of adding source lists of testing/unstable/experimental to production systems, I walked the long and painful path of backporting all (build-)dependencies and pushed them into our wheezy-backports repository.
If you want to give it a try on Debian wheezy, you could install the packages from our wheezy-backports repository:
# wget "http://ftp.cyconet.org/debian/sources.list.d/wheezy-backports-cyconet.list" \
-O /etc/apt/sources.list.d/wheezy-backports-cyconet.list
# aptitude update
# aptitude -t wheezy-backports install owncloud owncloud-mysql
For adding our archive key, you can just install the package "debian-cyconet-archive-keyring"