XL has no problem displaying negative times using the 1904 date system
(MacXL default) - choose Tools/Custom/Calculation, check the 1904 Date
system checkbox.

In article , "Ian"
wrote:

Your result is 5 hours as a proportion of a day displayed as a number, but I
don't see how you get a negative time in the first place. Negative times are
displayed as ####### in Excel.