Year 2000
Abbreviated as Y2k, the Year 2000 was a warning first published by Bob Bemer in 1971 that described the potential issues of IBM compatible computers using the two-digit date stamp. To save code space programmers created the dates to be represented by two-digits instead of four, i.e. 79 for 1979. When these computers roll over to 2000, the computer would interpret 2000 as 00, causing the computer to think it was 1900.
Several million dollars were spent on government and business computers upgrading the code and hardware to accept the year 2000. On January 1, 2000, no significant issues occurred being a success for some people and thought of as a hoax by others.
Also see: Bug