Year 1900 problem

The year 1900 problem is a problem understanding which century before or after year 1900 an event occurred. Unlike the year 2000 problem, it is not a problem tied to computer software alone, since the problem existed before electronic computers existed. Also in manual systems such problem has occurred.

The most common problem has been the issue how people's birthday has been registered. Often the birth year has been registered with two digits only, either assuming when designing the routine that it is not important exactly how old people are, or assuming that everyone is less than one hundred years old. In the late 20th century (before the year 2000), everyone alive at the time was born in the 19th or the 20th century.

In several countries, especially in Europe a national identification number was introduced (often in the 1950s) including information about the birth year, with two digits. The largest effect was that people 100 years old or more were mistaken for small children.

When handling the year 2000 problem, measures were sometimes done to avoid this problem, e.g. modifying the national identification number, even if the same problem already existed, the year 1900 problem.

Microsoft Excel

Microsoft Excel has its own year 1900 problem. It can't display dates before year 1900. This is not a problem associated with two digits year representation or similar. Microsoft Excel uses a floating point number to store dates and times. The number one represents January 1, 1900 (the number zero represents January 0, 1900 - which does not even exist). Quite simply the ability to display dates before 1900 is not included.

See also

* Time formatting and storage bugs
* Year 10,000 problem
* Epoch (reference date)
* System time