Per day calculation of basic and full salary for full and final settlement

Company has to pay me notice for 30 days basic pay and full salary for 15 days in F&F settlement.
Please help in calculating per day amount, should it be calculated by 30 days or 31 days
Basic/30 = perdaybasic
Or basic/31=perdaybasic
Company decided to choose 31 days to calculate per day salary which decreases my pay. Does any law help me here to calculate salary based on standard 30 days calculation?

also the bonus amount is not paid for the period I was working in the company stating the bonus will be paid only if the employee is working in organisation while the bonus is paid out even if the employee worked in the organization for the time bonus is calculated for. Request your advice.

Dear Juana,
For all purposes other than calculation of statutory gratuity, a month is deemed to comprise of 30 days only.
For gratuity, it is deemed to have 26 days.
Therefore, for the settlement of dues on full and final, the last month in which separation happens should be deemed to have 30 days only irrespective of the actual no of days in that month.
If an employee works for a minimum of 30 working days in an accounting year, he is entitled to get bonus for that year irrespective of the fact that he is in the service of the establishment on the date of payment of bonus or not. Hence the contention of the management is not legally correct.