With the date set incorrectly, many applications such as databases and scheduling utilities will behave unexpectedly, possibly causing data loss and corruption. Many applications are not equipped to properly handle a four digit year. To demonstrate how data gets corrupted, let's take a person's age for example.
Age is calculated by subtracting a person's date of birth from the current date.
Maybe, but probably not. In most cases, the PC will not change the date properly when the Year 2000 arrives. While recent versions of DOS and Windows support year 2000 dates, they only display the correct date when the system is left on. On these systems, when the computer is powered on in the year 2000, DOS and Windows get an incorrect date from the hardware. There are other problems with Year 2000 leap year support, Real-Time Clock compatibility, Y2K BIOS support and CMOS century settings.