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What is the Millennium Bug?

KD Morgan
KD Morgan

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.

On the stroke of midnight on January 2000, it was feared that all computers would shut down.
On the stroke of midnight on January 2000, it was feared that all computers would shut down.

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.

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Discussion Comments


My hometown is in Puerto Rico, and I was 9 at the time. ZDTV came to Dish network the year after its launch, and the millennium was hyped on pop culture (Talk about Jennifer Lopez's Waiting for Tonight and Backstreet Boys' Larger than Life).

I was so innocent that I had to take this kind of terminal threat seriously, even Medalla light claimed as "compatible with Y2K" (Just saw half of that commercial).

I even had the commemorative issue from El Nuevo Dia titled "100 aƱos de Noticias" (100 years of news). But as the Caribbean rang in the first few milliseconds of the new millennium, not even a light flicker occurred on an aging power system.


It was one of those things that was a huge mountain made out of a nearly non-existent molehill. I'll never forget the headline in my hometown newspaper on Jan. 1, 2000: "Y2K: OK!" Good grief. Has to be one of the most uninspired headlines I've ever read.

People were getting money from the ATMs and were stockpiling food, just in case everything went to pieces at midnight. My husband and I celebrated the New Year, watching the ball drop on TV, and figuring that, since Sydney, Australia and Paris, France, still had their lights on (they rang in the New Year several hours earlier than the U.S.), that we were probably going to be O.K. We were right, obviously. The 4-27-11 tornadoes were a much larger inconvenience, I can tell you for sure.


I remember watching with my brother that year when the clock turned to midnight Eastern Standard Time. We waited, so expectant, and then nothing happened. We looked around, not even a light flicker. So anti-climactic.

But then, at least our family hadn't bought a bomb shelter or anything to wait out the apocalypse that seemed so evident to some people.


I was living in Ohio at the time of the Y2K crisis, and there is a huge store near my parents' town called Lehman's that specializes in non-electrical appliances and alternative, old-fashioned things. They made a huge business and became somewhat nationally important, thanks to the paranoia and increased interest in owning wood-burning stoves.


When i was eight i thought it was a real bug that will get me or kill me electrically. i was young.

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    • On the stroke of midnight on January 2000, it was feared that all computers would shut down.
      By: Halfpoint
      On the stroke of midnight on January 2000, it was feared that all computers would shut down.