The expectation was that systems and programs that were in use in the 1960's, 1970's, etc. would have been replaced by the time the year 2000 came around. Thus, date arithmetic could get extremely confusing. For example, if you were born in 1935 and want to retire in 2000, the computer would determine your age in 2000 to be 00 - 35 which is minus 35, and not old enough to retire. To the top of this page Leap Year Problem Leap year calculations can cause a different potential problem. The year 2000 is a special case that only happens once every 400 years.
Some computer programs use a date field to trigger special actions.
When this special date occurs, the program takes some predetermined action. It might start using a new set of data, close our a file, send a special mail message, etc. In this case it is the fix of the year 2000 bug that can cause the problem. These computer chips are programmed to control the device. Unfortunately, these chips may have been programmed with dates in which the year was represented by only 2 digits.