Y2K means “year 2000” (K is a metric abbreviation for thousand). In the late 1990s the term was most often coupled with “problem” or “bug” to refer to a potentially disastrous computer programming peculiarity: Over decades of programming and in trillions of lines of code, developers had truncated the four-digit year to two digits as a space-saving mechanism, so that 1999 was rendered as 99. It was therefore feared that many computer programs, as well as simple chips in VCRs, watches, and other consumer devices, might malfunction, reading 00 not as 2000 but as 1900, or not recognize it at all. The problem was a concern for every sector of the global economy, but it was feared to have a particularly ruinous impact on the mainframe computer systems that are the backbone of operations for banks and other financial institutions, electric utilities, water systems, communication systems, oil and gas companies, and government entities (such as the Department of Defense and the Social Security Administration).

In the second half of the 1990s, business and government developed solutions to the Y2K problem, or the “millennial bug”; readiness was gauged periodically. To encourage the sharing of best practices across and between industries, the federal government passed the Year 2000 Information and Readiness Disclosure Act (signed October 1998). Despite assurances that the Y2K bug had been fixed, much of the public met the year 2000 with at least a bit of trepidation, some people having made emergency preparations such as stocking up on food and water, buying generators, and stashing away cash. Though there were isolated glitches, no major problem surfaced. Thanks to rectification efforts, the foretold Y2K crisis never materialized. But the cost of fixing the problem was high: it had an estimated $1.5 trillion price tag.