First go to Compass and make sure your session is saved in your browser cookies.
Then go to this link and download its contents. It should download as a .json file.
Upload that file here, select what extras you want, and hit generate. It'll generate you an iCal file you can import into your calendar software of choice.
Sometimes you'll get an error (Likely a 401) when trying to fetch your timetable. A known fix is clearing the cookies on Compass and trying again. If you can view your timetable in Compass then the timetable API link should work too.
This program runs fully client-side! Meaning: nothing "calls home", no data gets sent out, I can't see anything you do with your timetable. It all runs in your browser!
You can see for yourself by opening Developer Tools, going to the network section, and monitoring incoming and outgoing traffic. Other than loading this page itself, no other calls should be made.
If you're still unconvinced, run it offline :D
Additionally, I have no plans to maintain this forever, but the code is all on this one page (And on my GitHub repo) so go wild if you feel like it.