There's a reason why your phone's snooze alarm lasts for exactly nine minutes.

Image: iStock. 

You might do it a couple of times a morning. Maybe 10. Or you might not do it at all (in which case, colour us impressed).

Yep, we’re talking about hitting that snooze button and scoring some precious minutes of extra sleep time.

If you have an iPhone, you might have found yourself wondering why your snooze lasts for nine minutes exactly. Why not ten? Why not 15? Why not make it an even number, at least?

There is a reason for this seemingly arbitrary number, and it all comes down to history.

Certified iOS support expert Nic Lake says it’s because over time, clocks have snoozed for nine minutes because it was too difficult to set alarms to 10 minutes exactly. Bear with me.

“Early clocks and watches had gears that made it difficult to set a snooze for exactly 10 minutes. So they aimed for less than 10 minutes, aka nine minutes. Was a pretty standard thing till the ’50s,” Lake explained on the Q-and-A website Quora.

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“Then, when digital clocks came about, it was much easier to code in a nine minute snooze. All they had to do was take the last digit of the previous alarm (say, five), subtract one (now four), and set the new alarm to go off the next time that number came up. So, 6:45 –> 6:54, and so on,” he said.

Another user on the site, clock collector David Slavik, offered a second explanation.

Slavnik claimed the nine minute standard of modern alarms is because of hybrid electric clocks. These clocks physically flipped cards to indicate the time, and were driven by an electric motor.

“The problem is you still have a standard of 10 minutes. How this is explained is that when the user presses the buttons some number of seconds will have already passed. The snooze function had no way to deal with this and didn’t even try. So you end up with a function that is almost never quite 10 minutes, never less than or equal to nine.”

So, because of the time that has passed after you’ve hit the snooze button, the clock had to aim for the nearest minute — which was never exactly 10, but not nine. But somewhere in between. And the iPhone alarm is, at least according to Slavik and Lake, a tribute to that.

Something to think about next time you’re considering hitting that snooze for the seventh time in a row.

Fess up, how often do you hit the snooze button each morning?