Etesync

Etesync is a service where you can hold and synchronize your contacts and calendar information in a secure manner using End-to-End Encryption.

From the Etesync FAQ page:

Secure, End-to-End encrypted, and privacy respecting sync for contacts, calendars, tasks and notes with clients available on all major platforms. It creates a new account on your device to which you can save contacts and calendars. These are then synchronized across your devices in a secure way while maintaining a complete history of your changes both locally, and securely on our servers. After setup, you won't even know it's there. You just keep on using the same contacts and calendar apps you were using before.

Except that “and securely on our servers” is now “and securely in my server”.