Curfew?

Um, so, I was trying to figure out when students are actually supposed to be in their dorms.  I was reading the Hogwarts guide, and it said "at night" and "after dinner," but my question has to do with in the morning.  How early are students allowed to wake up and head out into the world?

I don't recall having an actual time set, but as a rule of thumb I'd say if they're out and about more than an hour before breakfast without a good reason (Quidditch practise for example) questions might be asked. In the summer, if they're up before it's light, that's definitely too early!

Thanks, that helps