DAVx⁵
CalDAV/CardDAV suite and sync app for Android
DAVx⁵ is a free, open-source Android synchronization application designed to connect calendars, contacts, and tasks with compatible online services. It uses CalDAV and CardDAV standards to synchronize personal information between Android devices and remote servers. The application integrates with Android's account and synchronization infrastructure, allowing information to appear in compatible calendar, contact, and task applications.