Japan added a leap second to its reference clocks on Wednesday morning, with no major disruptions reported to systems such as stock exchanges and air traffic control despite concerns over possible failures.
The National Institute of Information and Communications Technology, which manages Japan Standard Time, added another 60th second at 8:59 a.m.
As it was the first leap second to be added on a weekday in 18 years, the organization had called for a careful preparation since making the announcement in January.
When a leap second was last added, in 2012, failures occurred in several computer systems. The social networking service Mixi, which suffered from poor connections for four hours in 2012, reported no troubles this time.
Since the rotation of the Earth is inconsistent, clocks gradually fall out of sync with the movement of the heavens. Leap seconds fix that gap in the world’s reference atomic clocks.
A leap second “means Earth’s rotation sped up,” said NICT researcher Kuniyasu Imamura. “But it doesn’t mean it keeps accelerating. Only the Earth knows when the next leap second will be.”
A leap second was first introduced in 1972. The extra second was then added almost every year through the 1990s, but the insertion has become less frequent since 1999.
Imamura said some computer software cannot handle having 61 seconds in a minute, which can cause system failure. “So some operators break down the leap second and adjust the time over several hours or minutes, changing the length of a second itself.”
The Tokyo Stock Exchange sliced up the leap second and added it between 7 and 9 a.m. Trading commenced as usual at 9, and no major disruptions occurred.
The Ministry of Land, Infrastructure, Transport and Tourism said air traffic control was operating as usual.
Nippon Telegraph and Telephone Corp.’s two regional fixed-line telephone service units — NTT East Corp. and NTT West Corp. — inserted an extra second at 8:59:60 a.m. at their 117 speaking-clock services, and mobile phone carrier SoftBank Mobile Corp. also added the leap second to its service giving the time. The phone services NTT Docomo Inc. and KDDI Corp. broke down the leap second and added it to several hours or minutes before 9 a.m.
Radio-controlled clocks that correct time by automatically receiving information from signal transmitters during the night had a gap of one second after 9 a.m. Wednesday until they automatically checked on the time.