In short and very simple terms, some software stored date as DD/MM/YY.
It would asume that for year it would always prefix 19. The problem was when you reached /00. Any calculations or software decisions that happened based on that date, it would be off. Way off.
Some solutions where expanding the date to YYYY or adding a prefix to the new dates. Dates without the prefix would be 19xx. Date with the prefix X was 19xx and dates with prefix Y where 20xx.
Another solution was to set the prefix for 2-digit years on a sliding scale, so they are interpreted as a date within a specific 100-year period (date windowing). For example, see the 2029 rule: https://support.microsoft.com/en-us/help/214391/how-excel-wo...
This turned out to be one of the most cost-effective methods of fixing the problem, and was probably one of the most likely to be implemented. This was especially the case in situations involving software which ran closer to the hardware (for example, BIOS or firmware) or on systems where RAM or storage couldn't be increased and/or the change might increase the software's requirements beyond the system's capabilities.
There were a couple of computers in my shop that had a Y2K BIOS issue. Although there is a sort of software in the form of firmware on BIOS, many people considered this sort of Y2k error presentation a hardware problem.
So, while a Y2K compliance program dealt mostly with software, a complete program went through and tested all hardware in inventory.
the issue was a closed source problem, you could easily add the option to switch between 19 and 20 for calculations. or have a pre 2000 instance of the app and a post 2000.
In short and very simple terms, some software stored date as DD/MM/YY.
It would asume that for year it would always prefix 19. The problem was when you reached /00. Any calculations or software decisions that happened based on that date, it would be off. Way off.
Some solutions where expanding the date to YYYY or adding a prefix to the new dates. Dates without the prefix would be 19xx. Date with the prefix X was 19xx and dates with prefix Y where 20xx.