CalDAV Clients/Android

There are now at least four CalDAV implementations for Android:

CalendarSync Android CalDAV Click here
CalendarSync allows it to sync your device with various calendar informations sources. It also provides a lot of additional features. CalendarSync also allowes Android CalDAV sync.

If you are interested in translating the app in other languages please contact me.
 * 1) Using a self-created parser which support complex and more features than other iCalendar parsing/importing applications.
 * 2) Import appointments, alarms and attendees direct from iCal files (*.ics). and applications.
 * 3) Import appointments, alarms and attendees direct from Microsoft Calendar files (*.vcs) and applications.
 * 4) Export appointments, alarms and attendees which are stored on the device to iCal files (*.ics).
 * 5) Make a quick look at the appointments stored in the iCal files.
 * 6) Update old and add new appointments from an iCal file.
 * 7) iCalendar files are associated to this app.
 * 8) Timezone support.
 * 9) Create and remove calendars on the device.
 * 10) Fingerfriendly landscape/portrait mode aware GUI.
 * 11) Load, Parse and sync ICal files direct from the Internet from different sources.
 * 12) Supports the download/handling of calendar informations with HTTP/HTTPS.
 * 13) Supports the sync from and to server which provide calendar informations with CalDAV.
 * 14) Supports the download/handling of calendar informations with FTP/FTPS.
 * 15) Supports the download/handling of webcal/webcals feeds.
 * 16) Periodically background sync of calendar informations.
 * 17) Automatically background sync can be handled periodically by the app itself or it can be triggered by external applications like Tasker.
 * 18) Checking for updates
 * 19) Logging
 * 20) Advanced filtering which informations should be imported
 * 21) Supporting devices with more than one cpu core to speed up parsing/importing/downloading of informations.
 * 22) Multi-language: Currently english and german.

DAVdroid

 * 1) Set up SRV records and well-known paths.
 * 2) Install DAVdroid.
 * 3) Add a new account. If haven't set up well-known paths, use /caldav.php/user/ (see DAVdroid configuration].

Hypermatix CalDAV Clients/Calendar Sync for Android

 * Tries to synchronise the internal Android calendar store with a CalDAV server.
 * "Free as in beer" in the app store

aCal CalDAV Client for Android

 * aCal is a standalone calendar application which only supports calendars hosted on a remote CalDAV server.
 * "Free as in software" with the source code available on gitorious under the GPL v3 license.
 * The app store version of aCal is sold for a token NZD$2 (or equivalent) to discourage accidental installation by people who don't actually want a CalDAV client, and to help keep the author in beer and pizza.

caldav4j

 * the caldav4j-apk is a free replacement for the google calendar which syncs with remote CalDAV servers.

CalDAV-Sync beta and CardDAV-Sync beta(dmfs / Marten Gajda)

 * Synchronises the Android calendar with an arbitrary number of CalDAV servers.
 * As of version 0.1.4 two-way synchronisation is stable and no longer "experimental".
 * Available on the Android Market for ~2.50€ (as of 2011-08-28). CardDAV-Sync also comes in a free trial version.
 * According to the author it will be released as open source once version 1.0 is reached
 * Over a month of real-world use and not a single issue with it (User:Patrick Nagel)

Troubleshooting
If CalDAV-Sync and CardDAV-Sync don't sync or you cannot set up an account, check the following: $c->override_dav_header = "..." If that line exists comment it out or make sure it contains "addressbook" and "calendar-access". CalDAV-Sync and CardDAV-Sync won't sync if a collection is not advertised as calendar or address book by those headers.
 * You'll need at least PHP 5.2, for the DateTime class, since CalDAV-Sync seems to trigger the code paths for repeating events even if there are no repeating events in the calendar. (See also Setup_Failure_Codes/PHP_DateTime_class)
 * Verify that Keep-Alives are enabled in your web server configuration (they're disabled by default in the stock Apache config on RedHat/CentOS/Fedora)
 * Make sure you didn't change the DAV headers. Go to your DAViCal configuration file and look for a line beginning with

FLOSS CalDAV sync adapter by Gérald Garcia

 * Synchronise your calendar from a caldav calendar server.
 * Fully integrated and transparent in Android account management.
 * One way sync only for the moment.