The number of meetings I'm requested to attend has increased by roughly a factor of five over the last two decades. Instead of five meetings per week I'm currently having five per day on average. It thus doesn't come as a surprise that I depend on an electronic calendar to organize and get reminded of all these appointments.
On my desktops, I'm using the integrated calendar of evolution since seven years. Over the time, this implementation of a PIM for the Gnome desktop has proven itself to be reliable and stable, in contrast to Kontact, its KDE counterpart I've tried to use before.
In any case, having a calendar on my desktops is not sufficient anymore, as future appointments are typically arranged after Zoom meetings that I usually attend with my notebook. And even that is not enough: I may want to check my appointments on a whim in the middle of the night, where only my smartphone is immediately accessible. In either case, I do not need a full-blown PIM, but just a calendar client synchronizing with both owncloud/nextcloud and zimbra.
On Linux/GTK, I thought that gnome-calendar would be the natural candidate with this functionality. To my surprise it's straightforward to add an owncloud/nextcloud account with the associated calendar, but zimbra is not part of the online account collection of Gnome, nor is a generic CalDAV server. I found that almost impossible to believe, but it's in fact a longstanding bug (eight years!) that has still to be acknowledged and addressed by the developers. Fortunately, there's a simple workaround: after installing evolution and adding the zimbra CalDAV server there, it also shows up in gnome-calendar. Apart from this issue, gnome-calendar delivers exactly what I wanted.
This entire affair is a whole lot easier on Android. Davx5 available on F-Droid provides a convenient backend for any number of CalDAV servers, and any calendar app will serve as frontend. It works just as well as gnome-calendar on my notebook, but without any unexpected obstacles during the configuration of the calendars.
I'm now reminded of outstanding appointments wherever I walk and talk. That's progess! Or is it?