The millennium bug was a computer problem that threatened the operations of corporations, utility companies, finance industries, government agencies and even science. On the stroke of midnight between 31 December 1999 and 1 January 2000, the fear was that all computers had the potential of shutting down. The millennium bug is also known as the Year 2000 problem, Y2K problem, Y2K bug, and most commonly referred to as simply Y2K.
The millennium bug was specifically a programming problem. It was the result of a combination of a space issue as well as a lack of forward thinking on the part of the programmers back in the 1960s and 1970s. During the beginning stages of computer programming, memory and other storage space were scarce and expensive, so saving characters was a priority.
Programmers were writing business application code using COBOL (common business oriented language) and RPG (report programming generator) to run on mainframes. Programmers stored dates in the form of yymmdd which involved a total of six characters, automatically sorting in an ascending order. Each one of those characters equaled one whole space (byte) of computer storage. Consequently saving two bytes of storage for each date was significant when you consider the amount of date fields stored on cards, tapes, or disks in all the records in all the files in all the computers.
By the 1980s and 1990s programs were modified for changing business needs so programmers maintained, tweaked and added new requirements to the old applications, rather than rewrite them from scratch. The upgrades and modifications were enough to keep the original systems running.
During the mid 1990s, programmers started to realize that the dates would not sort correctly by the year 2000. Within the computer community it started becoming an issue which needed correcting. Then, in 1997, the situation became public knowledge.
A decision had to be made to either start over and rewrite the programs from beginning to end, or to fix the preexisting programs and stored dates. This option had another challenge because some of the source code had been lost.
Many companies were created to solve these problems. One option was to just add the century to the preexisting date. This would involve adding two more bytes for each date stored anywhere in their disk files. Others opted to rewrite their software and take advantage of the new networking and object oriented technologies as they moved their critical applications away from the mainframes.
Over 300 billion US Dollars (USD) were spent to correct the millennium bug. In addition to the software concerns, countless survival businesses sprang up and profited as a result of a concerned and proactive public.