Ever notice how on most clocks the 'snooze' feature is 9 minutes?  Even though modern day clocks are adjustable, the factory default setting is 9 minutes.  Why?

By the 1950s, all the innards of clocks were standardized.  The mechanisms were all the same.  The gears were the same as well.  Which meant the amount of teeth on each gear were the same in every clock.

Folb, Topical Press Agency, Hulton Archive, Getty Images

When clock makers had the idea of a 'snooze' button, because of the amount of teeth on those gears, they could only make the snooze length a little over 9 minutes or a little over 10 minutes.  Obviously, they went with a little over 9 minutes.  Why?

The second part of the answer has to do with the human brain.  When we start to fall into a deep sleep the body releases serotonin to help make us groggy.  Experts thought back then, as well as today, 10 minutes would be long enough for the body to release serotonin.  After 10 minutes, you would wake up groggy and in a bad mood.  So they decided to make the 'snooze' feature a little over 9 minutes.

Today, smartphones and most electronic clocks have adjustable snooze times, but beware, anything over 9 minutes may cause you to have a bad day.