This is a well-known, although intentional, "flaw" in the date system that
Excel uses. See this article:

http://support.microsoft.com/kb/214326/en-us

HTH,
Elkar


"faijaimond" wrote:

Excel has a general format for a date default to number of days since
1/1/1900. This is helpful in determining date differences. The only issue
is that Excel recognized 1/1/1900 as a leap year. If 1/1/1900 is subtracted
from 1/1/1901, the answer should be 365 days, but Excel yields 366. Excel
also recognized 02/29/1900 as a valid date, but this date does not exist,
hence there should only be 365 days in 1900.

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