I'm often asked what kinds of problems does Y2K create for
computers. There are basically four problems that non-compliant
computers have with Jan. 1, 2000.
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- It starts with a "2." Some programs, especially
data-validation routines, will only recognize years beginning with a
- It ends with zeros. Some random-number generators, which create
account numbers, for example, use the computer's system date and divide
by the last two numbers. These programs either lock up or crash when
they try to divide by "00."
- It starts on a Saturday. Many programs use a "day-of-week"
function to perform certain tasks. These can be as simple as an
automated back-up procedure to opening a bank vault if it is Monday but
locking it if it is Saturday or Sunday. The problem is that Jan. 1,
1900, was a Monday; Jan. 1, 2000, is a Saturday. If the computer thinks
the year is 1900 (as non-compliant systems will), the vault will swing
open on Saturday and lock shut on Thursday. This will affect any other
routines that use day-of-week calculations to perform certain actions.
- It is a leap year. Most people assume that every fourth year is a
leap year. However, every fourth turn-of-the-century is a leap year,
too. The year 1900 was not a leap year; the year 2000 is. Therefore, if
the computer thinks that the year 2000 is the year 1900, it will not
account for February 29. As a result, all kinds of calculations will be
off, including billing cycles.