World Wide Words

From the Turns of Phrase section

Millennium Bug

Also known as the millennium virus, millennium timebomb and Y2K problem (short for “Year 2000 Problem”). The potentially catastrophic risk, according to many industry experts, that a large proportion of the world’s computers will go wrong at midnight on 31 December 1999. This is because much of the programming code was written anything up to 25 years ago (what’s called in the business legacy code) when the century change was a distant prospect but a much more immediate problem was the shortage of memory and filespace. So years were commonly programmed using only the last two digits (“78” for “1978” for example). When the century changes, instead of moving on to 2000 all such dates will roll back to 1900, causing chaos in any system which compares dates, for example to calculate entitlements or penalties. As this includes a large proportion of the world’s systems, disaster is being predicted. The cure is to check every line of code for two-digit dates and change it, a process which is expected to cost business many hundreds of millions of pounds.