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