"October tenth is a Tuesday."
じゅうがつとおかはかようびです。 ← I'm surprised this isn't an accepted answer yet for this sentence, considering this sentence has been around since version 1.0 of the Japanese tree.
It did used to be the case that, for all sentences containing numbers, none of this kind of sentence accepted an all-hiragana sentence answer. It's great how the course contributors have added so many alternative answers that now cases of an all-hiragana answer being rejected for this kind of sentence has become a rare exception not the norm. ^^