Qantas, LinkedIn Sites Knocked Offline by Odd Bug

Dennis Faas's picture

Several major websites were briefly knocked offline this past weekend by a quirk in the calendar: a 'leap second' -- the rare additional tick added worldwide to clocks that fixes a natural flaw in our time-keeping systems.

The 'leap second' is used around the world on computerized time systems because a year on our clocks is slightly shorter than the actual the time it takes the Earth to go once around the sun.

Nowadays, we take most of our time signals from an atomic clock, which measures the vibrations of atoms in a metal called cesium so accurately that a one second error is nearly as large and glaring as a the 'leap day' we add once every four years.

Left uncorrected, this error would cause large time gaps to develop between our atomic clocks and the Earth's actual movements.

Extra Leap Second Catches Up

To correct for the inherent discrepancy between our clocks and the Earth's actual revolution around the sun, officials wait several years for the disparity to become large enough, and then add a 'leap second' to the calendar.

For various reasons, they add this extra second either at the end of June 30 or December 31. The last time we needed a 'leap second" was at the end of 2008.

But even adding a 'leap second' can create problems for very precise time-keeping systems. Although officials provide plenty of notice, sometimes computer systems don't adjust quickly enough.

As a result, some computers operate one second "off" compared with other computer systems around the world.

In some cases, this causes practical problems. For example, automated stock trades may show the wrong time and thus the wrong price. Some computers become so confused they stop working altogether.

Qantas Airlines A High Profile Victim

In 2012, the problem affected a number of companies. Australian airline Qantas, for example, had problems with its reservation software. At one point, the airline was unable to check-in passengers.

The problem was quickly detected and fixed, but it caused a backlog and delayed many flights by an hour. (Source:

Adding the leap second also caused problems with two technologies used by many websites: Java (a programming language used to add features to web pages) and Linux (an operating system used by the server computers that physically store websites).

Some major web sites hit by the leap second issue include LinkedIn, FourSquare, Reddit and Gawker. Mozilla was also affected, though its web browser Firefox continued working.

Google did not experience any problems coping with the leap second. The search giant says that it planned ahead for the leap second, and actually made the change with a series of tiny tweaks throughout the day. (Source:

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