Dear Saddy,
The formula for per day calculation is: Salary / Number of days in a month * Number of days present. The salary calculation is always based on the number of days in a month to the total number of days worked. Hence, for February, it would be 28 days, and the employee would be paid for 27 days, as a day would be deducted for absenteeism as noted by you.
Please do read this discussion exactly related to what you are asking. Blog your questions. [Monthly salary calculation for Feb and June with absenteeism deduction](https://www.citehr.com/71648-monthly-salary-calculation.html)
Regards, (Cite Contribution)