This year will be slightly longer after the Paris Observatory announced that it was adding a “leap second” to clocks.
At midnight on June 30, dials will read 11:59:60 for one second as clocks pause to allow the Earth’s rotation to catch up with atomic time.
Atomic time is constant, but the Earth’s rotation is gradually slowing by around two thousandths of a second per day.
It is the task of scientists and officials at the International Earth Rotation Service, based in France, to monitor the planet’s rotation and tweak time where necessary. Some years the Earth is on time and no adjustment is needed.
Software companies are bracing themselves for problems. When the last leap second was added in 2012 software and websites such as Mozilla, Reddit, Foursquare, Yelp, LinkedIn, and StumbleUpon all reported crashes and there were problems with the Linux operating system and programs written in Java.
Many computing systems use the Network Time Protocol, or NTP, to keep themselves in sync with atomic clocks. But most are not programmed to deal with an unexpected extra second.
Google has developed a special technique to deal with what it refers to as a “leap smear” by which it gradually adds milliseconds to its system clocks prior to the official arrival of the leap second. “The Earth is slowing down a little bit,” said Nick Stamatakos, the chief of Earth Orientation Parameters at the US Naval Observatory. “Atomic clocks keep very accurate time.”
The first leap second occurred in 1972, and it will be the 26th time in history one has been added to clocks. It means that the rotation of the Earth will have slowed 26 seconds compared with the time measured on atomic clocks.
Mr Stamatakos added: “For that day [June 30] there will be 86,401 seconds, instead of 86,400 seconds.”
Leap seconds are rarer now than when the practice began. From 1972 to 1979, at least one second was added every year. Leap seconds were added six times throughout the 1980s, but only four will have been added since 1999.
The US wants to get rid of leap seconds, claiming that they are too disruptive to precision systems used for navigation and communication.
Britain opposes the change, saying that it would forever break the link between our concept of time and the rising and setting of the Sun. It would also spell the end for Greenwich Mean Time, which is measured by the time at which the Sun crosses the Greenwich Meridian and was adopted in Britain in 1847.
Experts fear that once this link is broken it could never be restored because adding a leap minute or hour to global timekeeping systems would be virtually impossible.
