Funny, I am taking an American Sign Language course, and one of the components is talking about dates/days/weeks. Next Week, Next Monday, Last Tuesday, etc. I was talking to some of my classmates who were all struggling to fully understand when to use what sign(as was I), and I pointed out that talking about next Friday in English can get confusing depending on how each participant thinks about things.

Not surprised an LLM gets this wrong, lots of content consumed with various ideas on how these things should should work.