As Microsoft works to bring in the native support for CardDav on Windows Phone, an amateur developer, Viish has an app in place which supports CardDav Protocol. It allows you to sync all contacts from any server which uses CardDav. You can also add events into calendars for your contacts anniversary.
As the application is pretty new, not all CardDav provider might be supported. You will need to give it a try to put on your question at this forum thread.
Also as of now only server to phone synchronization is available. Two way Sync support is scheduled on next rerelease along with more language support.
Recently Google announced end of ActiveSync Support(January 30th) which is going to disrupt services like Google Calendar, Gmail & Contacts Sync.
However, Gmail does support sync over CardDav. So you can use your Google Account with the app, and see if your calendar sync works. Also If, you are an iPhone or iOS Users, the best test case will be iCloud.com which supports CardDav and you can sync cloud stuff with Windows Phone 8.
So till Windows Phone team officially rolls in CardDav Support in the OS, You can try out this app. I also urge the developer to bring in a trial feature so users can test it.