[horde] Old appointments got removed -- why?

[Christian Wolf]

Hello at everyone,

I use horde now since november or december 2015. I am pretty sure, that
I added appointments in 2015.

Now I wanted to look up some old events in 2015 and saw that there were
no appointments anymore. The first appointment is on 2016-01-04. As we
are in year 2017 now I am wondering if there is some automatic removal
in horde kronolith present. I found something in the settings but the
check box is not checked.
Was there maybe a bug and the box was not evaluated correctly?

I am using horde 5.2.16 and kronolith 4.2.18 at the moment. This is of
course only the actual version number. Also I see that there are
updates, which I will soon install.

Thank you very much
Christian Wolf