Why is a snooze nine minutes instead of ten?

On many, many clocks the snooze function is nine minutes instead of ten or five. Why oh why oh why is this the case. This is especially difficult since it has been suggested by many people that getting up on an odd number of minutes is bad luck.*

The thing is that I personally don’t use the snooze function. The problem is that if I had snooze then I would probably snooze forever. What I do is I turn my alarm clock off when ever it goes. This leaves me only one choice: get out of bed. When I used to be much more tired back in the bad old days I used to avoid snooze with it’s easy choices, and turn the alarm off but set a new alarm time of ten minutes from now. This gave me the extra ten minutes in bed that I needed and meant that I had made a conscious thought and so was at least partially out of my deep sleep.

So I was talking to my friend Alison who was wondering about why the snooze is nine minutes the other day, and I couldn’t remember the answer right away. I think this may be because there are about a million stupid reasons for it. The most common wrong reason is that digital watch makers wanted to only have to watch one digit of the clock and so made it be 9 minutes. This sounds pretty good. You would have to only remember one piece of data and watch for the number to be that again. But why not wait for it to be that plus one?

The real reason seems to be that it comes from analogue clocks. And that analogue clocks are slightly imprecise. And that the snooze was supposed to be 10 minutes or less. At first this meant that the snooze wheel ran for somewhere between 9 and ten minutes. But as the clocks became more and more intricate they became more and more accurate even with the snooze. At some point somebody decided to make it determined by the minute hand to add to the precision and at that point nine minutes was chosen as the largest number of minutes that is less than ten.

Then in the digital age when somebody was copying the clock they based it on this system. And then it got built into the National Semiconductor’s MM5370 digital alarm-clock chip which is used in most modern digital alarm clocks.

*Hey I don’t make these things up! People who think this, but want to use the snooze function, use this as an excuse to press snooze twice. Whereas this could be easily avoided by having the alarm clock go off one minute early (not that they’d ever do that).

3 thoughts on “Why is a snooze nine minutes instead of ten?

  1. Nick Ollivère says:

    I’m fairly sure my alarm clock has an 8 minute snooze. Normally, if I switch my alarm off instead of put it on snooze I go back to sleep and don’t wake up for half an hour – which can be bad. (By the way, maybe most are 9 because 9 is a circular number?)But more importantly than this I always set my alarm clock for an odd number. Is this the reason why I’ve been so unlucky? Instead of 8:30 I’ll set it for 8:31, and so on. I don’t know why. Maybe I think it’s more likely to work if it’s odd, and that the clock will forget it if it’s an ordinary number.

  2. Alex Andronov says:

    At first I thought that second bit sounded pretty crazy, but then I’ve realised that I only ever set my alarm at 15 minutes earlier. So if I was running late after waking up at 6:45 one morning then I would have to set my alarm at 6:30. Not that I’d have to as such – I just would.But on the circular number thing isn’t 9 not a circular number? It might be rounded in shape. Is that what you mean? Because a circular number (or Automorphic number) is one where the square of the number always ends in itself. Eg 5 is an Automorphic number. Because 5 x 5 is 25 (there’s a five at the end) and 5 x 5 x 5 = 125. And so on. But as we know 9 x 9 = 81. So no dice.

  3. Nick Ollivère says:

    I think what I meant was you can distribute the number evenly in a circle – which I don’t think you can, but maybe you can do this with all numbers?Anyway, I believe the explanation that derives from analogue clocks: they had to invent a gear whose teeth would mesh with the already existing gears: this was either 9 or more than 10.I do like the idea that the snooze function only works for 60 minutes and that 9 gives you the greatest amount of snooze periods in that time. More reasonable is that simply 5 minutes is too short, 10 minutes seems too long. It’s psychological. The same way prices are always .99p. No reason except to make us think it’s cheaper.

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