Year 2000 problem

The Year 2000 problem, also known as the Y2K problem, the Millennium bug, the Y2K bug, the Y2K glitch, or Y2K, is a class of computer bugs related to the formatting and storage of calendar data for dates beginning in the year 2000. Problems were anticipated, and arose, because many programs represented four-digit years with only the final two digits – making the year 2000 indistinguishable from 1900. The assumption of a twentieth-century date in such programs could cause various errors, such as the incorrect display of dates and the inaccurate ordering of automated dated records or real-time events. In 1997, the British Standards Institute (BSI) developed standard DISC PD2000-1 defining 'Year 2000 Conformity requirements' as four rules: (1) No valid date will cause any interruption in operations; (2) Calculation of durations between, or the sequence of, pairs of dates will be correct whether any dates are in different centuries; (3) In all interfaces and in all storage, the century must be unambiguous, either specified, or calculable by algorithm; (4) Year 2000 must be recognised as a leap year. It identifies two problems that may exist in many computer programs. First, the practice of representing the year with two digits became problematic with logical error(s) arising upon 'rollover' from xx99 to xx00. This had caused some date-related processing to operate incorrectly for dates and times on and after 1 January 2000, and on other critical dates which were billed 'event horizons'. Without corrective action, long-working systems would break down when the '... 97, 98, 99, 00 ...' ascending numbering assumption suddenly became invalid. Secondly, some programmers had misunderstood the Gregorian calendar rule that determines whether years that are exactly divisible by 100 are not leap years, and assumed that the year 2000 would not be a leap year. In reality, there is a rule in the Gregorian calendar system that states years divisible by 400 are leap years – thus making 2000 a leap year. Companies and organisations in some, but not all, countries checked, fixed, and upgraded their computer systems to address the anticipated problem. Very few computer failures were reported when the clocks rolled over into 2000. Y2K is a numeronym and was the common abbreviation for the year 2000 software problem. The abbreviation combines the letter Y for 'year', and k for the SI unit prefix kilo meaning 1000; hence, 2K signifies 2000. It was also named the 'Millennium Bug' because it was associated with the popular (rather than literal) roll-over of the millennium, even though most of the problems could have occurred at the end of any ordinary century. The Year 2000 problem was the subject of the early book, Computers in Crisis by Jerome and Marilyn Murray (Petrocelli, 1984; reissued by McGraw-Hill under the title The Year 2000 Computing Crisis in 1996). The first recorded mention of the Year 2000 Problem on a Usenet newsgroup occurred on Friday, 18 January 1985, by Usenet poster Spencer Bolles. The acronym Y2K has been attributed to David Eddy, a Massachusetts programmer, in an e-mail sent on 12 June 1995. He later said, 'People were calling it CDC (Century Date Change), FADL (Faulty Date Logic). There were other contenders. Y2K just came off my fingertips.'