I used DavDroid for months without problems but now the calendar synchronization keeps failing. I suspect that the reason might be a too old birthdate (year 1905). The birthdate is not true and I changed it to year 2000 but the synchronization error still keeps showing after every synchronization attempt. See the debug log: 0_1496398930267_debug.txt
Any help would be much appreciated.
ownCloud 9.1 (previous ownCloud 9.0 had the same error)