how to deduct number to a date

Thank you foe the quick response mohamed, as far a I know that's should be 6 years and 8 Months. Why is that there is a deduction in the months?
I have another question. How about if you will subract it to a certain year :

20 years 5 Months 6 days
+ July 6, 2005
________________________
( December 12, 2025 - 2400 days) <----- this here how will subtract this?

Thank you for the quick reply however, what I wanted to see is how you will subtract that number to the date as shown. Datedif just showed the subtracted value.
Example:
Date: June 01, 2033
- 6 years and 8 months (if converted to days it is 2400 days)

2400 days is just a sample number to be used to deduct from the specified date. Im trying to calculate days of stay in a certain jail of which the inmates are given privilege if they perform good then they will get an adjusted time allowance for their penalty.

But of course all these are just projections. Let me provide a more detailed information.

Expected date of release = June 01, 2033
Maximum imposable penalty = 20-0-0
actual time served = 5 years
time allowance earned = 6-08-0
total time serve: june 01, 2013 to may 31,2018

adjusted expected date of release: feb 23, 2023

can you help me on this humdingaling ?

Hi Sir,
If you are going to calculate the years served by the inmate, that should be 11 years, 11 Months and 19 days all in all.

Recapitulation:
Maximum penalty: 20 years
Date of commitment: june 1 , 2013
date of release based on imposable penalty is: june 1,2033
date of adjusted expected release: june 12, 2021
total time allowances earned: 11 years, 11 months and 19 days.

Just making a formula for this which is why Im trying to learn the basics in excel. The one showed is a projection of the formulation for computation