Traditionally, alarm clocks let you snooze for nine extra minutes — and there’s a surprisingly practical, historical reason for that. When GE-Telechron released the Snooz Alarm in 1956, the first alarm clock with a snooze feature, the clock’s mechanical design wouldn’t allow for a 10-minute extension. The gears lined up perfectly only after nine minutes, and engineers decided that was close enough.
It also turned out to be useful: falling back into deep sleep usually takes around 10 minutes, so nine minutes helped prevent oversleeping. Since then, nine has become the magic number, but that doesn’t mean it can’t be changed.
