The Year 2000 problem (also known as the Y2K problem, the millennium bug, the Y2K bug, or simply Y2K) was a notable computer bug resulting from the practice in early computer program design of representing the year with two digits. This caused some date-related processing to operate incorrectly for dates and times on and after January 1, 2000 and on other critical dates which were billed "event horizons". This fear was fueled by the attendant press coverage and other media speculation, as well as corporate and government reports. People recognized that long-working systems could break down when the "...97, 98, 99..." ascending numbering assumption suddenly became invalid. Companies and organizations world-wide checked and upgraded their computer systems.
While no significant computer failures occurred when the clocks rolled over into 2000, preparation for the Y2K bug had a significant effect on the computer industry. The fact that countries where very little was spent on tackling the Y2K bug (such as Italy and South Korea) fared just as well as those who spent much more (such as the United Kingdom and the United States) has generated debate on whether the absence of computer failures was the result of the preparation undertaken or whether the significance of the problem had been overstated.