From: mark@unicorn.com
Date: Mon Oct 26 1998 - 04:57:00 MST
William John [anthropy@inwave.com] wrote:
>*** WHY *** would any outages occur? How can a simple date cause such
>problems?
Here's a simple example: a few months ago Swedish engineers tested their
nuclear reactors for potential date problems. They discovered that any
date in the year 1999 caused a shutdown, because the programmers had used
a '99' date as some kind of end-of-data marker; this kind of thing is common
practice. I can hunt out the URL for the news story if you want it, but it
doesn't say much more than that.
Another: some equipment requires maintenance on a regular basis (e.g.
yearly), and when the date rolls back to 1900 it can get confused and shut
down for liability reasons. I've read of at least one piece of medical
hardware which has shown this problem, but don't have a cite handy.
On a more theoretical level, suppose you have two systems communicating
with each other, and the messages include a date. One is compliant, the
other isn't. The non-compliant system sends its data with a date of Jan
1st 1900, but the compliant system knows it's 2000. Hence this is clearly
invalid and it throws the data away. If that was important data, suddenly
your computerized control system fails.
There are many similar possibilities; no-one yet knows which will actually
happen or how bad the effects will be.
Mark
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