HXDrive Con&Cal

HXDrive Con&Cal (Contacts&Calendars) is an Android 4+ sync adapter for CalDAV/CardDAV. To use it, just add a HXDrive Con&Cal account for your CardDAV/CalDAV HXDrive server and your contacts/events will be synchronized in both directions.

App can be used for Personal or Business HXDrive solutions. If you are not HXDrive user, you can register your account with 3 GB of cloud storage for free !
https://www.hxdrive.com

One more usefull thing is that if you dont have smartphone, only tablet, but want to use Viber, WhatsApp, Telegram, etc... where that apps use phone card, you can sync your HXDrive Address book with your Tablet PC, and HXDrive Con&Cal adapter app will be recognized as real phone card, so then you can use Viber, WhatsApp, Telegram, etc ...