How to calculate between Years, Months and date by the given criteria

Hi,
I am working for Jail authorities in India and have an issue with automating the calculation of prisoner’s release. The criteria is like the prisoner does not get any remission for his under trail days, once he is convicted than he starts getting remission for 7 days a month, i.e he needs to work for the entire month starting form 1st of the month till the last date. If he is convicted on any other day apart from the 1st of any month he does not get any remission. The second criteria is if he completes the entire calendar year without any leave he gets one more month of remission i.e 30 days. How to automate it. We are currently doing manual calculations for it

Thanks for your time bebo021999, I am giving you an example for a guy who was convicted for 4 years. He was convicted on 04-05-2018. The undertrial period was for 2 Months and 29 days.
Now as he was convicted for 4 years on 04-05-2018 his release date without remission would have been 03-05-2022 i.e exactly 4 years form his date of conviction.
Now after he gets convicted he is given the setoff period for his undertrial days, in this case it was 2 Months and 29 Days. So we minus it from his exact date of release i.e 03-05-2022 that comes to 03-02-2022. Form here we start to minus his days months and years from the back date till the tally comes to zero.
Now in this case as he was convicted on 04-05-2018 we deducted 28 days from the 03-02-2022.
Now he will start getting a remission of 7 days per month.
As the criteria for remission is 7 days for the entire month completed i.e 1st till the last date of his month.
Now for any calendar year completed by the prisoner i.e from Jan to Dec he gets 30 days additional remission.
So in this case for the year 2018 he only earned remission of 49 days. i.e 7 months *7
For 2019 he got remission of 84 i.e 7*12 days plus 30 days as he completed the calendar year so the total was of 114 days.
For 2020 he got the same remission of 114 days
And for 2021 he got the remission of 21 days i.e for Jan, Feb and March as he was released on 3rd April 2021
Remission
2018 2019 2020 2021 Total
49 114 114 21 298

In short we calculate the above table manually and than do the manual calculation
Now his date for release would have been 03-05-2022 as he was convicted for 4 years on 04-05-2018.
After we minus the under trail days of the prisoner i.e 2 months and 29 days we get the date as 02-02-2022.
We apply the manual calculation as 2 months minus 03-05-2022 that comes to 03-03-2022 now we need to minus 29 days that comes to 02-02-2022 as the month of Feb in 2022 was of 28 days.
Now we minus his remission of 298 days so we minus 9 months i.e 270 days and the remaining 28 days from the date we got after deducting his under trial day. That is to minus 9 months from 02-02-2022 so we get the date as 02-05-2022.
Now we deduct 28 days from the 02-05-2021 we get the date as 04th April 2021.

Thanks for your time bebo021999
Yes we have a communication gap
Let me explain it this way.
The prisoner was undertrial from 12th Feb 2016 to 11th May 2016 then he was out on bail.
The court gave him the setoff period for his undertrial days when he got convicted for 4 years on 04-05-2018
So we calculate it this way, we put his release date manually as 03-05-2022 i.e 4 years.
Than from 03-05-2022 we minus his undertrial period i.e 2 months and 29 days so we get his release date as 03-02-2022.
From 03-02-2022 we start to minus his sentence served in prison starting with the first month that is without remission as he was convicted on 04-05-2018 he won’t be eligible for remission as the criteria for remission is for complete month.
So when we minus the sentence served in jail for the month for May 2018 we minus 28 days as he was convicted on 04-05-2018 and we minus it from 03-02-2022 so the calculation so far is

Actual date of release 03-05-2022 – 2*30-29 = 02-02-2022
We minus the 2 Months manually that comes to 03-03-2022 and the month of Feb in 2022 is of 28 days so after deduction the 29 days manually it comes to 02-02-2022

Now we minus his remission of 298 days
The remission break up of 298 days is as follows
Year 2018 from June to Dec i.e 7 months so 7months *7 = 49
Year 2019 From Jan to Dec i.e 12*7 = 84 Plus 30 days as he completes the calendar year so the additional 30 days for 2019
Year 2020 From Jan to Dec i.e 12*7 = 84 Plus 30 days as he completes the calendar year so the additional 30 days for 2020
Year 2021 From Jan to Mar i.e 3*7 = 21 as he is released in the month of April he won’t get the remission for April as the month is not getting completed
SO the total remission is 49+114+114+21 = 298
so we minus 9 months i.e 270 days and the remaining 28 days from the date we got after deducting his under trial day. That is to minus 9 months from 02-02-2022 so we get the date as 02-05-2022.
Now we deduct 28 days from the 02-05-2021 we get the date as 04th April 2021.
4th April been a Sunday he is released a day earlier on 3rd April