The Year 2000 bug, also known as the Y2K or Millenium bug, was the anticipated inability of many computer programs and embedded devices to handle year-dates later than Dec. 31, 1999. Many such programs and devices were constructed to interpret dates as running between 1900 and 1999, inclusive, and so lacked any way to represent years after 1999. Computer experts forewarned that when January 1, 2000 arrived, computers that were not "Y2K-compliant" would read the year 2000 as the year 1900. This was deemed likely to adversely affect huge amounts of software, particularly accounting and database systems, thus generating expensive errors or even shutting down systems. Since banks, power grids, nuclear power plants, water-treatment systems, and other industries were almost entirely computerized by 1999, it was feared that the Y2K bug might even trigger widespread societal breakdown.

No one knew exactly how serious or widespread the Y2K bug would be. Predictions ranged from...