Change your workbook's date system to the 1904 system
(Tools/Options/Calculate, check the 1904 date system checkbox). The
WinXL default 1900 system can't display negative time values.
Another option is to display the negative time value as a
text value in another cell while still using the actual
difference (#######) in any calculations.
Change your workbook's date system to the 1904 system
(Tools/Options/Calculate, check the 1904 date system checkbox). The
WinXL default 1900 system can't display negative time values.