Year 2000 problem
No valid date will cause any interruption in operations. Date-based functionality must behave consistently for dates prior to, during and after year 2000. In all interfaces and in all storage, the century must be unambiguous, either specified, or calculable by algorithm. 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.
Year 2000 problem-3