I’m sorry to hear that… DAVdroid is (only) a sync adapter - it does not handle or make any backups, because it’s not the scope of a sync app…
Deleting one instance of recurring event does not delete it from the server
I’m using DavDROID 1.9.5 with Nextcloud 11 on Android 5.1 with aCalendar.
I have a recurring event in the calendar. I delete it on the smartphone, it is removed from the calendar. But when I look at it via Thunderbird (Lightning) or the Nextcloud built in caleandar app, the event is not deleted. Instead, it is striked through.
Deleting it via Thunderbird or built in Nextcloud calendar app deletes the event.
When I look at the server logs (nginx), I see the following when deleting via DavDROID:
“PUT /owncloud/remote.php/dav/calendars/USER1/defaultcalendar_shared_by_USER2/a852616a-7b03-4e6f-bb4e-d1ce64097cda.ics HTTP/1.1” 204 0 “-” “DAVdroid/1.9.5-ose (2017/12/02; dav4android; okhttp3) Android/5.1”
When I delete it via Nextcloud app, I see the following:
“DELETE /owncloud/remote.php/dav/calendars/USER1/defaultcalendar_shared_by_USER2/a852616a-7b03-4e6f-bb4e-d1ce64097cda.ics HTTP/1.1” 412 324 “-” “Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0”
This was working not so long ago, as we moved from another app to DavDROID one year ago because of exactly the same issue.
here is the answer to your question:
Here is more to read about it:
The DELETE request will delete the recurring event with all instances and not just a single instance. To delete a single instance an exception (or EXDATE) has to be added to the recurring event which has then to be PUT back to the server.