Duolingo suggested "Second August-week". That's not normal in English. "Second week of August" is.
Honestly, I almost think Second August-week shouldn't be accepted as an answer. On one hand, yes, this is a german course not an english one. On the other hand, the sentence is so bad it should almost be unacceptable.
Doing this would also promote context-based translation, something a lot of people aren't familiar with, as they try to translate word by word.
I'm glad I'm not the only one who thinks "Second August-week" is bad English.