"Nos cepillamos los dientes en la noche."
Translation:We brush our teeth at night.
Why not in the night, it is a fair translation even if it seems a little spooky!
The unmentioned "our" It's unfair, that sometimes this kind of natural/obvious possession, when it's left out in Spanish is required in translation, and vice versa when it's left out in English, it's required in Spanish. The rule there is same in both languages.