Retro Software

What was the Millennium Bug and did anything happen?

what was the millenium bug
Photo by Erik Mclean on Unsplash

Also known as the Y2K bug, there was massive built-up to this in the 1990s. Some predicted an almost armageddon-like scenario but, in the end, little seemed to happen. What was the Millennium Bug all about and what actually happened?

What was the Millennium Bug?

In decades past, due to small storage capacities and expensive hardware costs, data was held in as compact a form as possible. Dates were one such item of data that could be shrunk. By not storing the century, a year could be just 2 digits (e.g. 71 instead of 1971). This was great because nobody thought the software of the time would still be running at a time when the century mattered. 

What nobody accounted for was the slow pace of change in big businesses – banks in particular. They built large, complex systems which, despite their creaking age, nobody wanted to re-write. So as the year 2000 approached, these shortened years were suddenly a concern.

Why? Well, it comes to down to when you do comparisons. Let’s say you have data for 1971 and 2002. Which came before which? Obviously, 1971 comes before 2002. But when you now say which came first out of 71 and 02… a computer will say 02.

What was likely to happen was that as the clock ticked over to 2000, computer systems will see it as the equivalent of 1900 and stop processing correctly. If you think about banks, this could means debits not being taken, cheques not being cashed, etc. Some even thought that this could lead to nuclear power stations shutting down (which is where we get to the armageddon scenarios).

There was also a lot of noise around “embedded systems”. As many devices have timer chips built in, it was thought that everyday items such as washing machines would suddenly stop working. However, this mainly turned out to be a giant red herring.

Why did everyone panic?

Because there was genuine cause to. If nothing had been done, software and hardware around the world might have done some unexpected things – particularly around money, which would have caused major economic problems.

However, the panic around embedded chips didn’t really help because, as I say, the millennium bug turned out to be quite an exaggerated issue in the end.

But, nothing happened when the Year 2000 came, right?

Oft quoted, the Millennium Bug is now seen by many as something blown out of proportion because “nothing happened”.

In reality, it’s estimated that over $300 billion was spent worldwide fixing it and is a perfect example of a potential disaster being diverted successfully.

How did we fix it?

It wasn’t what you’d expect, which is to add the century to these stored years.

What you have to remember is that expanding the size of a file or database to include the century is not as simple as you’d think. Every program that accesses that file has to be re-compiled, and thoroughly re-tested. Fixing the millennium bug was a huge undertaking already but to do that would have made it many times bigger. So, the solution was not to change the file, but any programs that did date comparison. That reduced the amount of code and programs changed, and reduced costs.

So, for example, if we use the previous example of 1971 and 2002. They would still be stored as 71 and 02 but code would now make a decision as to which century it was based on year. Let’s say that in this example there are no dates before 1970. Here, you’d change the code so that dates less than 70 would have ’20’ appended to it. Anything else would be prefixed with a ’19’. Only then would you compare the dates and, in this, case, it would now work correctly. This is known as date windowing.

But this in itself creates a problem, in that the issue hasn’t gone away – it’s just delayed. For the above example, let’s hope that the software has been replaced by 2070. However, some data windows were even earlier – 2020, for example (i.e. dates of less than 20 being 21st century and anything over that considered as 20th century – in this case, the year 2020 would then be seen as 1920). It’s highly likely that some companies have been tackling Y2K issues since, and will continue to do so for some time.

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About the author

David Artiss

Works for Automattic Inc., the company behind and Tumblr. Tech geek, international speaker and occasional PC Pro podcaster. Lover of Lego and video games.

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