In Excel’s date system,dates are serial numbersbeginning on January 1, 1900.
January 1, 1900 is 1, January 2, 1900 is 2, and so on.
More recent dates are much larger numbers.
For example, January 1, 1999 is 36161, and January 1, 2010 is 40179.
To display date values in a human-readable date format, apply anumber formatof your choice.
If Excel doesn’t display the date as a serial number it means the date is not correctly recognized.
Seethis articlefor more information.
This means the serial date 60 corresponds with the date 29-Feb-1900.
This problem makes certain date calculations in the year 1900 unreliable.
Date calculations after the first 60 days are reliable.
