"¿Sabes cuándo es el baile?"
Translation:Do you know when the dance is?
I was given
"Do you know when the dance is?"
as the translation, which sounds perfectly fine to me. Were you suggested an unnatural sounding sentence?
Your sentence wasn't accepted because you didn't include "sabes". Duo wants fairly literal sentences. Loose translations would require far too many alternative sentences.
In English, when you have a subordinate clause that starts with a question word and doesn't have a subject in a declarative sentence, then the verb can come at the end.
He knows how to juggle.
Her office is near the park where the free concerts are.
I know who it is.
However, when there is a subject, then the word order is back to normal
He knows why your dog eats what is not supposed to.
Her office is near where the city holds free concerts.
I know who John has been dating.
You are joking? This translation exercise is a short sentence and you think it's ok to use a completely different verb?!! Apart from the fact it's a completely different question. So Friday or next month is a reasonable answer to the given question whereas yours wants 08:30 type answer!!