I agree, it sounds strange a little. However it is hard to understand what is wrong.
Maybe the problem is: "в этот" needs previous context. That is: "В сентябре к нам приедет комиссия. В этот месяц я буду работать до восьми вечера.".
That is "в этот" doesn't work without context, while "в этом" means "in the current ..." by default.