Tell HN: You can't create a top folder named “Calendar” in Office365 Outlook

My employer is moving from GMail to Office365, so I'm trying to recreate my folder structure in Outlook. The first folder I tried to create was "Calendar". But creating it didn't work. No error message, it simply didn't get created. At first I thought creating folders doesn't work, but then I tried creating folders with other names, and they worked. Also, creating this folder inside another folder works, but not at the top-level.

It turns out you can't create a top-level folder called "Calendar", or whatever you call "Calendar" in the language you have set for the UI. If the UI language is Polish e.g., then you can create "Calendar", but not "Kalendarz".

I just thought it's a funny bug, so I'm sharing it here.