Overtime Calculation

hi everybody,

actually i was doing an audit for a client. there is a scenario for overtime calculation is like

(Basic Salary/30)/81.5No of Hours

based on this calculation employee will get loss in the month of february why bcoz no. of days in that are 28.

based on this calculation employer will get loss in the months of 31 days

am i right? correct me if i am wrong.

now the client want to change that 30 days to the number of days of that month.

how to write this rule.

inputs will be highly appreciated