I’m in the process of backing up some data, and I thought it’s a good opportunity to get rid of a lot of stuff I’ll never look at again. In the process I’ve come across this bit of trivia – I didn’t even know there is a 9-minute interval (which is not too surprising given that I never use the snooze function 😉 ).

Well, one might think that nine minutes are the approximate length of time it takes to fall back asleep before being roused by the piercing beep of the infernal alarm clock. But as it turns out, it’s partially a matter of mechanics. Back in 1956 when the snooze button was first introduced, alarm clocks had standardised gears. The snooze gear had to mesh with the teeth of the other gears. Due to the configuration of the gears, a nice, round 10-minute snooze cycle was out of the question, so the engineers had to choose between 9 minutes or 10-plus minutes. As we all know, punctuality is a virtue, so the engineers went with 9 minutes.

Apparently there’s another explanation too for modern digital alarm clocks. Being set to 9 minutes, the clock only needs to watch the last digit of the time. So, if you hit snooze at 6:45, the alarm goes off again when the last digit hits 4 – at 7:54. They couldn’t make the snooze period 10 minutes, or the alarm would go off right away – alternatively the clock would take more circuitry.

Various attempts have been made to change the 9-minute snooze cycle — manufacturers have tried 5, 7, and 10 minutes, but a 9-minute snooze has become the unofficial standard.