How old is Hermione Granger in Harry Potter and the Deathly Hallows?

I had always thought she was the same age as Ron and Harry. But is she a year older? The reason I ask is because I remember her birthday being in September, after Harry's. But she has to do a lot of outside of Hogwarts magic before September in Deathly Hallows, for example their escape from the death eaters on the Night of Bill and Fleur's wedding (which happens in August right after Harry's birthday.) Wouldn't the trace still be on her if she's not quite 17 yet? And the Voldemort-controlled ministry able to find them?