Safari Version 18.0 (20619.1.26.31.6) as installed by the new macOS Sequoia release does not display the calendar for me after the upgrade. The rest of the site seems to render perfectly fine.
This does seem to only be affecting Safari.
Safari Version 18.0 (20619.1.26.31.6)
Thanks!
I am also seeing this issue with Safari 18.1, it seems like they broken something with the WebKit rendering in Safari only and I’m not sure the cause yet.
Thanks for confirming that I’m not just seeing things!
I signaled this via direct message and email to Trakt’s support and have had zeo answer or acknowledgment. 
This started with iOS/iPadOS/macOS beta and should have been solved, or at least acknowledged by now.
I really prefer the web version of calendar to the app’s, where it requires many clicks.
It no longer works on Safari on the Mac, but also on the iPhone and iPad.
I pushed a Safari fix and the calendar is rendering correctly for me now. Please let me know if it’s working for you as well.
It started working last week on my iPhone and now works correctly on my iPad and Macs.
Thanks! And have a great day.