As I understand it, it's been more or less "accepted" that September 1st is the date that determines which year of Hogwarts you're in. But I also do not believe this has been explicitly confirmed anywhere.

Looking only at things JK Rowling has written or said, what do we know about the cut-off date? Has it been said anywhere? If not, what are the closest bounds we can establish based on known character birthdays? (If using birthdays be careful to demonstrate that the year of the birthday is itself known, and not just derived from the assumption that Sept 1st is the cut-off.)

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    Given that 1st Sept is the first day of the academic year in real world UK schools, it's fair to say that Rowling simply used that in much the same way she based much of the mundane minutia of wizarding education on regular the British education system. Feb 4, 2022 at 3:34
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    Interesting side question here: how can Hogwarts be based on the UK educational system, when it predates that system (as we know it) by a couple centuries? I'd ask it, but I more than half expect there's no supportable answer...
    – Zeiss Ikon
    Feb 4, 2022 at 15:47
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    @ZeissIkon It is just the other way around, the Muggle education system is simply based on Hogwarts. The Statute of Secrecy didn't go into effect until the late 1600's so there was plenty of time to share notes...
    – Skooba
    Feb 4, 2022 at 15:52
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    @ZeissIkon - perhaps the in-universe UK educational system doesn't realise that it is based on the Hogwarts timetable?
    – AdamT
    Feb 4, 2022 at 15:52
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    @ZeissIkon - 1 century difference. Hogwarts was founded in the 10th century, Oxford University (and education for younger students base their timetables on those of universities) was founded in the 11th century. Hogwarts may have altered their timetable to match the Sept - July year that real schools use when it was introduced, so the transition from primary education to wizarding education was more seamless. Feb 4, 2022 at 16:39

2 Answers 2


We can bound the cutoff date to prior to September 19th and after July 31st.

This can be confirmed through:

  1. Hermione's birthday, stated to be September 19th on JKR's old website.
  2. Hermione being older than Harry as she takes her Apparition test, which you must be 17 to take, during the Spring of Half Blood Prince (HBP22) and Harry does not (he was one of only a few students in potions class).

So this would bound the date between Harry's birthday of July 31 and Hermione's birthday of September 19 since they are both in the same Hogwarts year. This means that Hermione missed the cutoff and is almost a full year older than Harry (316 days to be precise).

I am not aware of an exact date being stated anywhere in canon materials...

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    Well, no wonder she's such a smarty pants! She's nearly a full year older. All those extra books she read waiting to start kindergarten gave her a huge head start!
    – FreeMan
    Feb 4, 2022 at 17:16

We can understand that the "cut-off" age is September 1st, from the note about apparition lessons In HBP chapter 17:


If you are seventeen years of age, or will turn seventeen on or before the 31st August next, you are eligible for a twelve-week course of Apparition Lessons from a Ministry of Magic Apparition instructor.

We know that students eligible for apparition tests are in year 6, because it says (In chapter 18):

...the sixth-years' first Apparition lesson

Therefore the dates determining the grades are September 1-August 31.

  • Shouldn't it have just said "for all sixth years" then?
    – ibid
    Feb 10, 2022 at 18:53
  • Even if the statement "the sixth years'" is taken literally and not just a generalized simplification, all this really shows is that the students with birthdays before September 1 are all in sixth year. It doesn't exclude the possibility of some other students in sixth year born on September 2, for example.
    – Zayn
    Feb 10, 2022 at 18:56

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