Excel's Historical Bug: Why 1900 is Incorrectly Treated as a Leap Year
By
susam
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Summary
Microsoft Excel incorrectly treats the year 1900 as a leap year due to a historical compatibility decision. This bug originated from Lotus 1-2-3's assumption that 1900 was a leap year, which Microsoft maintained in Excel for backward compatibility. The article explains why this behavior exists and outlines potential issues if the bug were to be corrected, noting that it causes minimal harm to most date calculations.
Key quotes
· 4 pulledMicrosoft Excel incorrectly assumes that the year 1900 is a leap year.
When Lotus 1-2-3 was first released, the program assumed that the year 1900 was a leap year, even though it actually was not a leap year.
This made it easier for the program to handle leap years and caused no harm to almost all date calculations in Lotus 1-2-3.
When Microsoft Multiplan and Microsoft Excel were released, they also assumed that 1900 was a leap year.
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