Why was Y2K specifically a big deal if computers actually store their numbers in binary? Why would a significant decimal date have any impact on a binary number?

Question

I understand the number would have still overflowed *eventually* but why was it specifically new years 2000 that would have broken it when binary numbers don’t tend to align very well with decimal numbers?

EDIT: A lot of you are simply answering by explaining what the Y2K bug is. I am aware of what it is, I am wondering specifically why the number ’99 (`01100011` in binary) going to 100 (`01100100` in binary) would actually cause any problems since all the math would be done in binary, and decimal would only be used for the display.

EXIT: Thanks for all your replies, I got some good answers, and a lot of unrelated ones (especially that one guy with the illegible comment about politics). Shutting off notifications, peace ✌

In: 478

Answer 1

This isn’t an issue of the ability to store a number, but of the space allocated to store a number. There are two issues at play here. First, computers have an issue known as a stack overflow error. Second, older programs had limited resources with which to work, and tried to save space wherever possible. And programmers try to use all kind of tricks to minimize the resources used to store information. And when the trick has an error, it can result in stack overflow, when a number rolls all the way from its maximum number to 0.

This is the reason pac man has a kill screen, why a radiation machine killed a patient when it falsely thought a shield was in place to limit exposure, why patriot missiles early in the Gulf War missed their target when the launcher was left on for over a month, and more.

The y2k issue was only relevant because programmers in the 80’s thought that 2 digits was enough to hold the date. 81 for 1981, 82 for 1982.

Except when we go from 1999 (99) to 2000 (00), the program with its 2 digits thinks 1900. And if that program was tracking daily changes, for example, suddenly, there’s no date before it and the check fails, crashing the program.

So 1999 to 2000 has no importance to PCs… but it had have a huge limitation to programs that used a shortcut to save precious limited resources. And overcoming y2k involved updating those programs to use a 4 digit number, removing the weakness.