
Why does the alarm clock snooze button give you nine extra minutes, not ten? - peteforde
http://www.straightdope.com/columns/read/1361/why-does-the-alarm-clock-snooze-button-give-you-nine-extra-minutes-not-ten
======
DanBC
> "Or maybe, since the clock is counting (typically) the power cycles from the
> wall socket, it's because [...]

> Engineer's comment: Nice try, bub, but clocks don't count that way.

What? Some clocks do count that way. That's why you can buy converters.

[http://www.electric-clocks.co.uk/60hz50hzfrequenc.html](http://www.electric-
clocks.co.uk/60hz50hzfrequenc.html)

> Thiis module takes the 60Hz input and produces a 50Hz output to ensure the
> clock keeps the proper time. The module is supplied with 9vac via a UL
> listed power supply adapter. The clock has had it's coil rewound to work at
> 9vac.

> No changes to the movement - no altered wheelwork. If the clock is ever
> required to run in the UK it is as simple as providing 9vac from a UK 50Hz
> power supply and bypassing the convertor.

[https://en.wikipedia.org/wiki/Electric_clock#Synchronous_ele...](https://en.wikipedia.org/wiki/Electric_clock#Synchronous_electric_clock)

> A synchronous electric clock does not contain a timekeeping oscillator like
> a pendulum, but instead counts the oscillations of the AC utility current
> from its wall plug to keep time.

Here's a nice page telling you how to build one. It has plans for both 50 Hz
and 60 Hz.
[http://sound.westhost.com/clocks/sync.html](http://sound.westhost.com/clocks/sync.html)

~~~
nodata
So instead of measuring vibrations from a crystal, they are measuring cycles
from the wall? Why?

~~~
exDM69
In the past, the mains AC frequency was a cheap and accurate way to keep track
of time. A lot of devices relied on the mains frequency.

Why does your modern day LCD monitor have a 60 Hz refresh rate? It's legacy
from 1950's vacuum tube televisions that synced their beam with the mains
voltage frequency.

~~~
X-Istence
The AC frequency used to be very inaccurate, it was only through a lot of work
and legislation that it was made accurate, specifically so that electronic
devices could use it to keep time.

Nowadays the electric companies want more leeway in how they run their grids
and would love to have the frequency be less accurate, trying to keep it
accurate actually costs a lot of money, since now as load changes on the grid
they have to make sure to spin up new capacity. As the load increases the
frequency goes down, as load decreases the frequency goes up. It is a careful
balancing act that is required for the power companies to keep it within spec.

If it was allowed to drift more the power companies wouldn't be required to
spin up more capacity that then goes unused.

------
BarkingOven
I'll tell you exactly why it's nine minutes. Because in the olden days where
everything was made with discrete components, the math of 9 minutes is WAY
cheaper.

Let's say it's 6:00, and you hit the snooze button. Save the current value of
the minute minus 1, into a comparitor, Trigger the alarm when the comparitor
goes off automatically.

If you save the current value into the comparitor, the alarm triggers
immediately. Now you need to add delay logic. Just use current minus 1, since
it's only a few half-adders.

You can't use the high order minute digit because then your snooze length will
depend on your current low order minute digit. Any logic to compensate starts
adding a multiple of the number of components required.

~~~
troels
But are clocks using a base-10 counting system? I'm thinking no.

~~~
colomon
The oldest digital clock my family had used a mechanical display, so it had
ten values for the right-most digit, six for the next, and twelve for the
left-most. So this explanation would definitely make sense for it.

But I don't recall if it actually had a snooze button...

------
atoponce
I can't say if this is why it's 9 minutes, instead of 10, but when the alarm
goes off, and I hit the snooze, my brain is anything but fully conscious. So,
I see the time "06:00" then "06:09" rather than "06:10", and I know the time
has changed- because of the 9. At the next interval, it's "06:18" rather than
"06:20". Again, an obvious time differential for my brain. Instead of just 1
number changing every ten minutes, 2 numbers are changing.

06:00 06:09 06:18 06:27 06:36 06:45 06:54 07:03 ... etc.

Versus:

06:00 06:10 06:20 06:30 06:40 06:50 07:00

Not enough numbers are changing for my brain to latch on in its semi-conscious
awake state, if the time is only changing by 10 minutes. Changing by 9, and
it's clear the time has changed, and it's a new time. Thus, I'm not thinking
only 10 minutes have passed, when the truth is that 40 minutes has actually
passed.

~~~
contingencies
This seems closer to engineer-thought reality, IMHO.

Also, some people like to snooze multiple times... a low number of times, to
be precise. They do this as a regular thing.

If I were such a person and I were to snooze thrice, I would know I am really
in need of getting up if 30 minutes has elapsed. There is an up to one minute
procedural loss on sorta-wake-up, activate-limb, smash snooze button, go back
to bed. So I know I'm definitely not sleeping over my 30 minutes of triple-
snooze allowance if I have a 9 minute timer. (Yes, the timer could be set from
the trigger time rather than the re-snooze time, but at least some ancient
embedded devices probably did not function in this way)

To further compound this line of thinking, we should remember that getting out
of bed is not the only use for timers. Another would be kitchen timers where
people might really, really, really want to get the pie out before it burns
and some default allowance for human fuzzy foibles is therefore a useful
feature.

Perhaps we should replace the title of this post with: _Engineers: "Nine; it
made sense at the time"_.

------
MRSallee
8:00:00 am

alarm clock begins beeping

8:00:15

I actually begin waking up

8:00:45

I manage to get up and silence the dumb machine

8:10:00

alarm wakes me up again after initial snooze, ten minutes after I intended to
be awake

If the snooze went in ten minute increments, and a person was fond of
snoozing, after a handful of snoozes the time delay between alarm sounding and
snoozing would add up and throw off the mental calculation.

"I've hit the snooze five times, it must be 8:50, oh shit it's actually 8:55,
FML," versus, "I've hit the snooze five times, it must be 8:50, oh hey it's
actually only 8:47."

~~~
hrkristian
That's a good theory.

I have multiple alarms on my phone, as sometimes I'll turn off an alarm
completely in my sleep. I put these alarms teen minutes apart, call it OCD.
Snooze time of nine minutes makessense a lot of sense fire my part.

~~~
andyhmltn
I do this. I set one alarm for an hour before I'm meant to be up (I usually
don't remember this), one half an hour before, one on the actual time and then
in smaller and smaller increments until I'm so annoyed with turning it off
that I just get up.

------
Juha
How about this for a reason: One of the first big snooze clock manufacturers
choose 9 minutes for some random reason and the rest followed thinking: "There
must be a reason they choose 9 minutes, it sounds specific. Lets have our
snooze be 9 minutes too."

I was expecting find some some highly researched psychological quirk to be the
reason in the post. I guess reality is just more random and coincidental.
Reminds me of the way QWERTY came to be the standard
([https://en.wikipedia.org/wiki/QWERTY#History_and_purposes](https://en.wikipedia.org/wiki/QWERTY#History_and_purposes)).

~~~
ordinary
That does not explain anything though, it just moves the problem. As the
article also points out, what was the original "random reason"?

------
Groxx
Dunno. All the alarms I've owned have been 6 or 7 minutes.

Another question: why does the alarm clock blare non-stop until you turn it
off, rather than beeping a couple times and then going silent, giving you a
moment to get up and turn it off without annoying the living hell out of
everyone who doesn't have to get up?

Current theory: alarm clock designers never marry.

~~~
TeMPOraL
Depending on how tired (or drunk) I went to bed the previous night and how
much time I gave myself for sleep, it might take even a few minutes for me to
finally wake up to the alarm signal. Anything short would be totally
ineffective for me.

Also, this ensures the alarm clock does its job - either you wake up yourself,
or your angry family members wake you. Both ways, you get up when you wanted.

~~~
Groxx
Agreed. So progressively get more annoying, instead of doing the worst
possible thing first.

------
failrate
I have a problem with this explanation, because on my grandmother's ancient
electromechanical clock (with radium painted hands), the snooze alarm interval
was user-defined between a few minutes to almost an hour. I'm leaning towards
someone cleverly using the numeric rollover to trigger the interval, and then
every subsequent digital clock cargo culting the design.

------
therandomguy
I thought it was to disorient you a bit. If you typically snooze three times
you know you have to be out of the bed at 8:00 sharp (with 7:30 original).
Easy for your brain to latch on to that. Now with 9 mins…

~~~
aeontech
I can do multiplication in half-conscious state easily if it means a few more
minutes of precious, precious sleep...

Besides you really just need to remember how to do subtraction, not even the
multiplication table

    
    
      var snooze = 3
      snoozety (30) minutes minus snooze (3) minutes = twenty seven
    

Now, if the alarm clock required you to solve a calculus problem, that'd be a
bit more challenging :)

------
blahedo
I've been using my cell phone as primary alarm clock for years, and it always
bugged me, for reasons I can't even articulate, that the snooze interval was
"wrong"\---ten minutes on one phone, five on another. When I finally got my
Android phone and could find my own alarm app that let me configure the snooze
time, I was _inordinately_ pleased. 9 minutes it is. :) (Alarm Clock Plus, by
the way---has a few other nice UI features as well.)

------
pgrote
A shame you cannot get to the old link in the article.

[https://web.archive.org/web/20021001101305/http://users.rcn....](https://web.archive.org/web/20021001101305/http://users.rcn.com/jayman/)

~~~
toomuchtodo
[http://web.archive.org/web/20000830091714/http://www.ultrane...](http://web.archive.org/web/20000830091714/http://www.ultranet.com/~jayman/)

------
ctdonath
I want to know why the alarm clock off button is built like something you'd
not want to use. Snooze is a big fat easy button; off is a small switch hidden
among other switches and usually on the bottom back of the device, requiring
turning off to stop the alarm and then turning the switch back on to re-enable
it for the next day. Once I'm awake, I want to shut the alarm up - period -
without having to find and fiddle with a hidden control. Or am I seriously
missing something obvious about standard cheap alarm clocks?

~~~
_wmd
Because for people like me, unconscious zombie-like bears who will dig through
concrete walls with bare hands in order to quiesce the source of the
disturbance of my crucial slumber, while maintaining no memory of the
demolished wall should I be successfully woken 10 seconds later, easily shut
off devices simply have no effect.

I've woken up a few times on the floor curled around the power cord to the
alarm clock, torn from the wall (or to find a phone in 15 pieces and a new
dent in the wall).. many, many people like me

------
dwrtz
It leaves you with an extra minute to decide if you're going to hit snooze
again.

------
Steuard
I always guessed that they wanted something around 10 minutes, but they wanted
more than one visible digit to change each time to make it more obvious that
time had passed. (That is, a sleepy person might be more likely to mistake
"7:20" for "7:00" than they would be if they saw "7:18".)

But that wouldn't be relevant with old analog alarm clocks, which evidently
had a 9-10 minute snooze, too.

------
tsotha
I always assumed this was a function of hardware on the original snooze-
enabled digital clocks. If you reset a decade counter chip (like the CD4017),
you get a rising edge on the carry out pin after nine clocks.

------
rgf
I always thought it was 9 minutes to have 10 minutes of total delay with 1
minute ring time. So that if you don't do anything it keeps ringing every ten
minutes.

If you hit snooze it just stops ringing earlier.

I think it's optimised to ring periodically in the worst case scenario (when
you don't wake up). With earlier snooze it's just easier to keep the 9 minutes
worst case implementation, instead of taking into account the time you hit
snooze and adjust the snooze time to reach the 10 minutes total delay between
rings.

------
jalanb
I came to the comment page to say that it's pages like that that make me
grateful for the internet.

Then I read the comments - actually, it's pages like this that make me
grateful for the internet.

------
platypii
I have always assumed it was to reduce the likelihood of conflicts with future
alarms. For example if I set alarms at 8:00 and 9:00, if I've been snoozing
the 8:00 alarm, and snooze is 10 minutes, the two alarms will both fire at
9:00. With 8 or 9 minute intervals that is much less likely, and so its easier
to see that maybe they are two different reminders. This probably applies more
to phones than old school alarm clocks however.

------
koobz
Nine is great. I snooze 4 times and it's 4 minutes more time I have than if it
were 10 minute intervals. That's 4 extra minutes to ride my bike to work on
time for the daily standup at my startup.

Now I suppose I could just set my clock 36 minutes later and get 36 minutes of
quality sleep. But I think I actually enjoy those short snooze button dreams.
And I savour every minute. Again and again and again and again.

------
tempestn
I had always just assumed it must have been an ease of implementation thing.
(Explanation 8.) Their suggestion that you could just check the 10s column
instead of the 1s is misleading. You would have to test both the 10s and the
1s column to get a 10 minute differential, unless the original alarm time
happened to be a multiple of 10.

------
brechin
My clock DOES have a ten-minute snooze. I know previous clocks I've used had a
9-minute snooze, but currently when my alarm goes off at 6:00, I hit snooze a
few seconds later, then a few seconds after the clock displays 6:10, it alarms
again.

------
splinter_head
On an old alarm clock of mine, the snooze started at 9 minutes, then went down
to 8, then 7 and so on. this allowed exactly 45 minutes of snooze. Something
from that may have been brought into modern alarm clocks?

------
striderhiryu
Maybe just because it takes around one minute from the time the alarm starts
to ring and the time the sleepy-head presses the button and eventually gets
up. Better have a minute earlier than later.

------
erichurkman
I prefer to subscribe to the idea that it was an off-by-one error myself.

------
MiguelJones
Maybe it's just a simple matter of whoever implemented the snooze
functionality picking 9 minutes as the value. The one minute difference
between 9 and 10 minutes is probably negligible.

------
codezero
This still skips the reasoning for even an imprecise 9 or 10 minutes. What
information guided that decision? Ignoring the precision is a separate
practical issue.

~~~
jarrett
I can imagine it went something like this:

Engineer: "Hey boss, how long did you want the snooze timer to run?"

CEO: "Oh, I don't know. Not too long, not too short."

Engineer: "What does that mean? Like 10 minutes or so?"

CEO: "Sure, I guess that would be fine. Just get it done."

Since this is an alarm clock, not a nuclear power plant, it's entirely
conceivable that the decision was made very casually. It could have just been
someone's gut feeling that 9 or 10 minutes felt right.

~~~
codezero
Sounds about right, but it would be awesome to know for sure, but maybe I
should be getting something done too :)

------
aiaf
I set the snooze on my phone alarm to 20 minutes, which is the standard for
the Uberman polyphasic sleep practice. Feels good enough.

------
redblacktree
Mine is adjustable. I have it set to 3 minutes. I still often snooze 5-6
times, but now it costs me ~20 minutes instead of an hour.

------
benatkin
Is there a good documentary about alarm clocks?

------
jbrooksuk
I was wondering this, just this morning as I hit snooze. Thanks HN, you've
done it again!

------
smoyer
A nice parallel to the question "Why do I click on a floppy disk to save my
file?"

~~~
jmpe
Oh, there are a few more like that:

\- there's a very good chance that the touch-pad in your new laptop uses the
PS/2 protocol to communicate with the system

\- why do I need to address cylinders/heads/sectors in a flash block device? I
can understand sectors (block addressing) but cylinders and heads? It's
FAT/EXT4 legacy, but the translation layer is still there in many OS-es.

\- I recently wrote a driver for an LCD. I could have sworn I was accessing a
CRT: front porch, h-sync pulse, back porch, v-sync, ...

------
happywolf
I always wish iOS allows me to set the snooze interval...

------
napolux
My alarm clock gives me 8 minutes. Now what?

~~~
mrweasel
Every single alarm clock I've had has given me seven, and I always wondered
why.

------
badman_ting
Moral of the story: Worse is better :)

------
zvrba
Am I the only person who manages to wake up almost instantly and never uses
the snooze function?

