Descriptions : DAVx⁵ (formerly known under a different name) is the only all-in-one synchronization solution for your contacts (CardDAV), calendar (CalDAV) and your tasks (based on VTODO). The app is easy to set up and can be perfectly integrated into your preferred calendar / contact app (including standard apps). It can also be used separately if you have either CalDAV, CardDAV or just tasks.
Features :

+ Two-way synchronization (server ↔ client)
+ Native Android 4+ implementation
+ Flawless integration with your device and your favorite apps
+ Easy setup
+ Fast algorithms for high performance
+ Optimized for phones and tablets
+ Super safe and we respect your privacy!
+ DAVx⁵ is completely open source

Required Android Versions : KitKat [4.4–4.4.4] - Lollipop [5.0–5.0.2] - Marshmallow [6.0 - 6.0.1] - Nougat [7.0 – 7.1.1] - Oreo [8.0-8.1]

Download DAVx⁵ CalDAV CardDAV Client v2.6.4-gplay APK Final Paid Free

DAVx_.ver.2.6.4-gplay.build.331.apk