June 30 will be one second longer than usual thanks to the leap second. Although it may seem like a tiny, insignificant change, it could potentially wreak havoc on some computer systems not ready to handle this adjustment.
According to Bob Ivry and Yuji Nakamura of Bloomberg, human timekeeping has been independent of the earth's rotation since 1967, when the clocks went atomic. To account for the change in the earth's slowing rotation, scientists will add a second to keep everything in sync.
"The system is only as strong as its weakest link," Greg Wood of Futures Industry Association said. "There are going to be issues."
Bloomberg reported that scientists have added leap seconds 25 times since 1972. The most recent adjustment happened in 2012.
"It's scheduled for 8 p.m. [ET] in New York, just when markets in Asia are opening, and exchanges around the world are taking no chances," Ivry and Nakamura wrote. "U.S. stock markets are ending some after-hours trading early and others from Sydney to Tokyo are recalibrating their clocks ahead of time."
Geoff Chester, public affairs officer for the U.S. Naval Observatory in Washington, told Bloomberg that about 10 percent of large-scale computer networks could encounter problems due to the leap second. The agency keeps time for the U.S. military.
"With the leap second, you count 61 seconds in a minute, and that's where the problems lie," Chester said.
Bloomberg elaborated on how the time will be made in sync to account for the leap second.
"Earthlings have to make sure NTP, or Network Time Protocol, used by computer systems, meshes with Coordinated Universal Time, or UTC, which is determined by the oscillations of cesium-133 in atomic clocks," Ivry and Nakamura wrote. "UTC is currently one hour behind London time."
To adjust to the leap second, Bloomberg reported that futures exchanges will smear the leap second after the event in Australia, Singapore, South Korea and Japan. The leap second will occur around the same time the trading day begins in Asia and Australia.
"Some exchanges are taking no chances," Ivry and Nakamura wrote. "They plan to chop the leap second into 7,200 pieces and smear it over two hours."
Peter Whibberley, a scientist at the UK's National Physical Laboratory, told BBC News that leap seconds "depend on measurements of the Earth's rotation, which varies unpredictably." He emphasized that given the irregular nature of leap seconds, plans have to be made.
"Leap seconds are announced only six months in advance," Whibberley said. "This means computers and software cannot be supplied with leap seconds programmed in, and they must be inserted manually."
Whibberley warned of the consequences of not getting leap seconds right the first time.
"Getting leap seconds wrong can cause loss of synchronization in communication networks, financial systems and many other applications which rely on precise timing," Whibberley said. "Whenever a leap second occurs, some computer systems encounter problems due to glitches in the code written to handle them."
According to BBC News, proposals have been floated to ditch the practice of adding leap seconds, given their problems with computer networks. Members of the International Telecommunications Union are expected to discuss the issue in Geneva this November.
"We need to stop having this fire drill every few years," Wood said, comparing the leap second to the Y2K event. "I'm in favor of it not occurring midweek."