Enable "Developer mode" in Settings -> Developer tools to install the Terminal app.

Open the terminal app and type the following:

devel-su
pkcon refresh
pkcon install nemo-qml-plugin-calendar-qt5-tools
exit

Download the schedule and import it:

curl -o fosdem.ics https://fosdem.org/2019/schedule/ical
devel-su -p icalconverter import fosdem.ics

We need to import with devel-su because:

  • Importing as the user nemo won't work due to permissions
  • Importing as root will import to the wrong calendar file
  • icalconverter lacks an option to choose which calendar

The output should be something like this:

[nemo@Sailfish ~]$ devel-su -p icalconverter import fosdem.ics
Password: 
Enjoy your privileges.
[W] unknown:0 - sqlitestorage.cpp: 193 - database "/home/nemo/.local/share/system/privileged/Calendar/mkcal/db" opened
[D] unknown:0 - Successfully imported: "fosdem.ics"

Restart the calendar app and take a look at Feb 2nd to 3rd. Enjoy!

P.S. I made a script which saves you from most of the typing:

chmod +x Downloads/fosdem.sh && Downloads/fosdem.sh