Harry Potter: Hermione's Time-Turner Was Slowly Killing Her

Harry Potter: Hermione's Time-Turner Was Slowly Killing Her
Image credit: Warner Bros.

Every time Hermione Granger used her Time-Turner, it aged her more. How dangerous was that, and how much could she have aged in one school year?


  • Time travelers still age at a normal rate even when they’re in the past.
  • Hermione Granger consistently used her Time-Turner which made her age.
  • According to our calculations, Hermione was 12-13 days older than she should have been by the end of The Prisoner of Azkaban.

The Time-Turners appear to be a great idea, especially for those who severely lack in the sleeping department or need to rescue their convicted godfather from a fate worse than death. Allowing their users to travel back in time and do something they didn’t do the first time, the Time-Turners are a great asset, but a dangerous one, too.

What Are the Obvious Dangers of the Time-Turners?

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The main risk related to the use of the Time-Turners was clearly stated in Harry Potter and the Prisoner of Azkaban. A Time-Turner’s user can never allow their past self to see them; otherwise, something terrible will happen. The space-time continuum breaking, the past self going clinically insane, or something along these lines.

This fact alone explains the restricted and heavily monitored distribution and usage of the Time-Turners: all it takes for a tragedy to happen is one fool who can’t follow simple rules. But apart from messing with the timelines, more dangers await those who actively use these artifacts, and these effects add up dramatically over time.

What Are the Hidden Dangers of the Time-Turners?

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Albert Einstein suggested that a time traveler would only be able to return to the moment when they used the time machine plus all the time they spent in the past — but not the exact moment they used it. Why? Because time is relative. The time traveler would continue aging even in the past, and their chronological age would need to catch up to their new biological age.

In the Wizarding World of Harry Potter, the Time-Turners didn’t work this way, and time travelers returned to the exact moment they used them. What this means is that every single time Hermione Granger (the only character who we know consistently used the Time-Turners) traveled back in time, she aged more than she should have.

How Much Did Hermione Age Thanks to Time-Turners?

Let’s do some quick math — sorry, some quick Arithmancy to determine Hermione Granger’s “new” biological age at the end of The Prisoner of Azkaban.

A school year in Hogwarts is 10 months, but the Christmas and Easter holidays take away one entire month. This leaves us with nine months or (roughly) 36 weeks.

At the end of the year, Hermione dropped two extra classes which returned her to the normal number of hours, which means she used her Time-Turner for two subjects. But she also dropped Divination right before Easter, meaning that before that, she had not two, but three extra classes she had to travel back in time for.

As a side note, Hermione’s additional classes were Arithmancy, Ancient Runes, and Muggle Studies. But let’s keep Arithmancing our way through her busy schedule. For the sake of convenience, we’ll first calculate as if she only had two additional classes and then add the hours she aged before dropping the Divination classes.

Two classes, each (presumably) twice per week since they’re not core subjects, and one lesson is around 1.5 hours. That’s six hours per week multiplied by 36 weeks. This brings us to 216 additional hours which translates to nine days. Now, let’s add the third subject into the mix.

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Hermione dropped Divination before Easter which means she attended it for six and a half months or 26 weeks. Let’s say these classes also took place twice per week, meaning she aged for just over three days from her third subject alone.

According to our calculations, Hermione Granger aged just under 13 days more than she should have thanks to using the Time-Turners. That’s not even two weeks of her life added up; even if we double the numbers, that’s still less than a month. Thankfully, she didn’t get to use her Time-Turner any more than that.

But guess what? In the end, she was still younger or the same age she was supposed to be thanks to being petrified for around 21 days during the second year.