BUG: 1900 Feb 29th is a valid date for MS Excel 2007 but it is not existing

Question

BUG: 1900 Feb 29th is a valid date for MS Excel 2007 but it is not existing

Anonymous

I have found a bug on MS Excel 2007: the date 1900 Feb 29th is present as a valid date (serial number = 60), but 1900 (as well as all years divisible by 100, but not by 400) is not a leap year.

To find it, plase enter 01.01.1900 in A1 cell and then A2 = A1+1, A3 = A2+1, etc...

Is this a known bug?

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Answer 1

This is by design; this error has been present in all versions of Excel for Windows.

When Microsoft introduced Excel for Windows in 1987, Lotus 1-2-3 was the dominant spreadsheet program, and Lotus 1-2-3 counted 1900 as a leap year. To win over Lotus customers, Excel had to be 100% compatible with it, so the developers deliberately built this error into Excel too.

Once Excel had become the major spreadsheet program, there were so many workbooks in use that removing the error would break many existing spreadsheets, so it was left, and it's unlikely that it will be removed.