Leap year bug stops computer systems across Japan

Some of Japan's most sophisticated technology proved vulnerable on Tuesday to the little- anticipated "leap-year bug".

Some of Japan's most sophisticated technology proved vulnerable on Tuesday to the little- anticipated "leap-year bug".

It was not mayhem on the scale some predicted for the turn of the millennium - with the Y2K bug - but computer system failures across Japan showed that such glitches were not just the invention of unemployed programmers.

The biggest disruption to daily life was the refusal of more than a thousand post office cash machines to boot up in the morning, but there were no panic withdrawals and most of the machines were fixed by early afternoon.

The Meteorological Agency's data-gathering system misreported weather conditions in the country. Citizens of Kyoto were told of heavy rain, but those preferring the evidence of their own eyes left home without their umbrellas. There were also failures in seismographs, which are used to predict tidal waves and detect earthquakes.

The nuclear industry, which experienced some difficulties over new year, reported no serious problems. However, a computer system failed at the Monju nuclear facility in western Japan, which has not been operational since a nuclearaccident in 1995.

The leap-year bug is caused by a convoluted misunderstanding. The computers apparently recognise that 29 February does not simply come around every four years - it is cut out if the year is divisible by 100 - but did not know it was reinstated if the year is divisible by 400. They therefore thought 29 February was 1 March.

The Japanese government admitted to having let its guard slip after the much-feared Y2K bug proved to be mostly a non-event. As the only country in the world to experience significant problems, it might have further damaged its reputation for technical expertise and enhanced its reputation for official negligence.

Mikio Aoki, the chief government spokesman, said yesterday that because the new year passed virtually without incident, "there is no denying we were negligent this time".

Elsewhere, few problems were reported yesterday. New Zealand had minor problems in the banking sector, and in the Netherlands there were small, temporary interruptions to internal communications at the Dutch Meteorological Institute.