Is Hermione Older or Younger than Harry?

[Robert Jones]

No: HPFGUIDX 92501

We know from the books that Harry was born on July 31st and that 
Hermione was born in September (her parents gave her an early 
birthday present so she could buy stuff in Diagon Alley).

But was she born in the same year as Harry or the previous year?  
That is, is she one or two months younger or ten or eleven months 
older?  No great plot point turns on this, I was just wondering.

Bobby