More than you might think. And not just to Usain Bolt. Ask anyone who was flying with Qantas on Sunday when Amadeus, the system the airline uses, had technical issues. Several hours were spent with staff having to turn to manual processes to check passengers in. Although it hasn’t been specified what caused it, there’s a chance it could be down to a leap second issue – where there has to be a one-second time adjustment to synchronise atomic clocks with those based on the Earth’s rotation.
Time is important, of course. As James Gleick memorably pointed out in his fascinating book “Faster: The Acceleration of Just About Everything”, the nanosecond can now be measured, and this has led to practical results:
“The time-obsessed used to keep their watches accurate to within seconds; now they keep their computers accurate to within milliseconds. Nanosecond precision matters for worldwide communications systems. It matters for navigation by Global Positioning System satellite signals: an error of a billionth of a second means an error of just about a foot, the distance light travels in that time. One nanosecond – one foot. That is a modern equivalence worth memorising.”
Suddenly, being a minute late for dinner, a meeting or that conference call seems to take on a bigger significance…

Qantas gets rocked by Amadeus • The Register.