"가장 좋아하는 요일이 언제예요?"
Translation:What is your favorite day of the week?
I think the use of 요일 indicates a day of the week, instead of a favourite day(날)< which can mean birthday, national day, labour day, any day of the year etc
Just to clarify:
WHAT is your favourite day of the week: 가장 좋아하는 요일은 무슨 요일이에요?
WHEN is your favourite day of the week: 가장 좋아하는 요일이 언제예요?
언제 does mean when, that threw me off two. I think there are too many ways to interpret a sentence and still be correct.
Because they used the word 요일 to specifically mean which day of the week, eg Saturday, Sunday, Monday etc. If you asked someone their favorite day and just used 일 or 날, their answer could be Christmas or their birthday, so it's more vague.
I said, "What day is your favorite?" It was marked wrong but reported it.
You are wrong. Don't just report anything you get wrong. 요일 is for days of the week.
I think part of the confusion is that many Americans (myself included) usually say "day" to mean "day of the week." I can't recall ever saying "day of the week" in a way that could also include the weekend, which seems to be what's happening in this practice sentence.
So the practice sentence is very awkward for me as well, and there's no way I'd have gotten it "correct" if I hadn't seen the desired translation beforehand. English is my native language, and this is not how I would ever express this question.