This bug is related to the ITA language pack of Scrivener. I took me a while to me to understand why this wont work:
should be formatted to something like “thursday, 2021”, but instead I get “thursday,”
The hint text suggests to use “aa” for the year portion of the date. Then, I thought about “year” being usually expressed as “yy” and changing the format to “EE, yyyy” finally worked.
So, to keep it short, the language pack incorrectly translates the year format.