Depending upon the terms and conditions of the employee, they are classified as daily rated, weekly rated, fortnightly rated, or monthly rated. The calculation of wages is also done accordingly. If your case is related to a monthly-paid employee, then there is no question of 30 or 31 days as you have agreed to pay him a certain amount per month. A month means a calendar month extended from 28 days to 31 days, i.e., the total available days in the particular month. In case of full attendance, he is entitled to get the same monthly wages. However, in case of absence without pay on some working days, deductions may be made on a proportionate basis. For example, if a monthly-rated employee is without pay for 3 days in Feb., Mar., and Apr., then the wages may be calculated as follows: Feb - Monthly rate/28 x 25, Mar - Monthly rate/31 x 28, Apr - Monthly rate/30 x 27.
You may post any particular case in detail if not satisfied.
Regards