Days remaining/overdue formula

I am trying to make a status sheet for aircraft that reflects time remaining on replacements, inspections etc. I have accomplished this base on hours of operation and cycle times but the calendar items are throwing me for a loop. based on what i've found so far, this formula, =IF(H20<B4,B4-H20,B4-H20) returns an accurate number in days:

H20= 11/10/1986
B4= 11/1/2020 (FUTURE DATE)
RESULT= 12410.00 (34 YEARS)

How can i have the result display a negative (-) in front of this number to show that this number is overdue?
How can i change this formula to also calculate "days remaining" without a negative

i would like for this to be displayed in the same cell, as this is the way i am copying the information off that looks like a complicated database output
Lastly, i would like to change the output to whole months, so the number is not so scary.

Thanks for any advice you can give me, i have attached the file, i think

adding spreadsheet

Does this give you what you want? Put this in cell J20 and copy it down:

=IF(H20>$B$4,DATEDIF($B$4,H20,"M"),-DATEDIF(H20,$B$4,"M"))

Gregb11,
Thank you that is exactly what i needed.