Translation:When are the holidays?
In this sentence, is "het" functioning as "it" rather than the"? Because "vakantie" is a "de" word. I mean, does "Wanneer is het vakantie" mean something like "When is it holidays"?
Yep. Your analysis is correct. :)
My answer was: "When is IT vacation" which was considered wrong by Duolingo. I reported it. Another possible translation could be: "when is it vacation time".