Year 2000 Problem (Y2K)
Definition - What does Year 2000 Problem (Y2K) mean?
The year 2000 problem (Y2K) was a problematic situation faced by digital (and some non-digital) files and systems due to the practice of using the last two digits instead of four digits when indicating the year in a date. This resulted in 2000 indistinguishable from 1900 by an affected system. This particularly affected machines dealing with real-time events and display of dates.
The year 2000 problem is also known as the Y2K bug, millennium bug, Y2K problem or century meltdown.
Techopedia explains Year 2000 Problem (Y2K)
In order to save memory, early computer and electronic digital devices were programmed to use only the last two digits for year. This turned out to be a costly error, because the year 2000 was seen by these machines as the same as 1900. An estimated amount of $300 billion was spent to update systems before December 1999 to make them Y2K compliant.
The Y2K problem caused a great deal of concern, and some outright panic, in the time leading up to January 1, 2000. Some believed that nearly everything powered by computers would malfunction or simply cease to function, including banking systems, power grids, traffic lights and communication systems, leading to chaos.
While there were some documented malfunctions due to the Y2K problem, they were relatively few and did not cause widespread problems.