The Intentional Date Bug
Category: General Weirdness | [Item URL]
A primary goal of computer programming is to write bug-free code. But did you know that Excel programmers created an intentional bug?
It's true. According to Excel, the year 1900 is a leap year. So if you enter the following formula, Excel won't complain, even though 29 February, 1900 is not an actual date:
=DATE(1900,2,29)
The reason for this error is compatibility. In the early days of personal computing, Lotus 1-2-3 was the most popular software available. Lotus programmers made the leap year mistake, and Microsoft programmers reproduced it so they could use the same date serial number scheme as 1-2-3.
Therefore, the days of the week prior to 1 March, 1900 are incorrect (e.g., 28 February, 1900 is really a Wednesday, not a Tuesday as report by Excel). In actuality, this is not a big deal because Excel doesn't even support dates prior to 1 January, 1900 -- which itself is an oddity.
Microsoft claims, perhaps rightfully so, that fixing the bug would create
many more additional problems.
Excel Oddities
Excel is a complex program, and has been around for a long time. Consequently, it has many obscure nooks and crannies to discover. Some of them are described here.
Keep in mind that some versions of Excel are odder than others. In other words, the things described here may not apply to all versions of Excel.
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