Y2K: Taste of things to come in leap year shutdown

By Chris Barton

The electronic date change problem does not just happen at midnight 1999 - it can bite when you least expect it, even on days that do not exist.

There are at least five other dates which could bring computers to a standstill.

The New Zealand Herald experienced just how unpredictable the problem can be when at midnight, February 28, all the editorial PCs suddenly locked up with a red screen helpfully advising:

"Sorry, an uncontrollable error has occurred. Operating System Timer or date is invalid!"

Technicians roused from their slumbers managed to quickly remedy the problem by restarting the PCs and manually changing the date. But then the head-scratching began.

Why were the PCs showing the date as Monday, February 29, 1999? The leap year and the extra day in February are not due until 2000.

So far no one can explain the glitch which is all the more puzzling because it has occurred after an extensive year-2000 upgrade of the IBM OS/2-based software.

A spokesperson for IBM said it had not come across the problem before and calls to other OS/2-based sites in New Zealand found they had come through February 28 unscathed.

But the glitch does illustrate how date changes can lock computer systems. It is also a reminder that midnight, December 31, 1999 is not the only date to worry about. Other dates likely to cause concern include:

* March 31, 1999 - when accounting systems roll over to the new financial year. Some will not work because they see the date field "00" as 1900, not 2000.

* 22 August 1999 - the day global positioning system (GPS) satellite clocks roll over to their week 10,000 which their computers will read as "0000".

Washington-based management consultant Rick Barry, due in New Zealand later this month to run workshops, said: "Clocks on the GPS report time as a number of weeks since the launch of the system in 1980. On 22 August, this counter will overflow and return to 0000. Systems or equipment that use GPS signals may malfunction."

* September 9, 1999 - Mr Barry says 9.9.99 will have a special and unintended meaning in many computer programs, because 9999 is a common programming device to signal that a stack of data had reached its end.

* February 29, 2000 - an "uncommon leap year" which many programmers may not have understood. Similarly, December 31, 2000, the 366th day of the leap year, could cause further problems.

* October 10, 2000 - 10.10.2000, the first two-digit day, two-digit month and four-digit year may throw an unforeseen spanner into some programs.